Create a Message changedapi/messages/create
Nearest release: v2.1.283, published 3 hours after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
Recorded here
Lines+179added
Lines−197removed
From line
139
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First seen
14 Aug 2026
this site's first read of the page
Recorded edits13to this page, all time
The whole hunk
from line 139, old and new numbered
/
from line 139
139139
140140 - `document_title: string or null`
141141
142 maxLength: 500, minLength: 1
142 minLength: 1, maxLength: 500
143143
144144 - `end_char_index: number`
145145
from line 159
159159
160160 - `document_title: string or null`
161161
162 maxLength: 500, minLength: 1
162 minLength: 1, maxLength: 500
163163
164164 - `end_page_number: number`
165165
from line 183
183183
184184 - `document_title: string or null`
185185
186 maxLength: 500, minLength: 1
186 minLength: 1, maxLength: 500
187187
188188 - `end_block_index: number`
189189
from line 207
207207
208208 - `title: string or null`
209209
210 maxLength: 512, minLength: 1
210 minLength: 1, maxLength: 512
211211
212212 - `url: string`
213213
from line 363
363363
364364 - `title: optional string or null`
365365
366 maxLength: 500, minLength: 1
366 minLength: 1, maxLength: 500
367367
368368 - `SearchResultBlockParam object`
369369
from line 427
427427
428428 - `name: string`
429429
430 maxLength: 200, minLength: 1
430 minLength: 1, maxLength: 200
431431
432432 - `cache_control: optional CacheControlEphemeral or null`
433433
from line 463
463463
464464 For a toolset member tool_use, the toolset family this member belongs to.
465465
466 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$
466 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]+$
467467
468468 - `ToolResultBlockParam object`
469469
from line 499
499499
500500 - `tool_name: string`
501501
502 maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$
502 minLength: 1, maxLength: 256, pattern: ^[a-zA-Z0-9_-]{1,256}$
503503
504504 - `cache_control: optional CacheControlEphemeral or null`
505505
from line 527
527527
528528 The caller-assigned identifier for this tab, unique within the inventory.
529529
530 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
530 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
531531
532532 - `title: string`
533533
from line 553
553553
554554 Tabs opened and download state changes during this call. "Nothing to report" is expressed by omitting the field, never by an empty list.
555555
556 maxItems: 200, minItems: 1
556 minItems: 1, maxItems: 200
557557
558558 - `BrowserStateChangeTabOpened object`
559559
from line 571
571571
572572 The `tab_id` of the opened tab, present in `tabs`.
573573
574 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
574 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
575575
576576 - `BrowserStateChangeDownloadStarted object`
577577
from line 583
583583
584584 The caller-assigned identifier for this download, stable across the state changes reporting it.
585585
586 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
586 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
587587
588588 - `url: string`
589589
from line 604
604604
605605 The caller-assigned identifier for this download, stable across the state changes reporting it.
606606
607 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
607 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
608608
609609 - `url: string`
610610
from line 616
616616
617617 Where the executor saved the file, on the executor's filesystem. Only included when another tool in the same environment can read the file at that path.
618618
619 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
619 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
620620
621621 - `size_bytes: optional number or null`
622622
from line 634
634634
635635 The caller-assigned identifier for this download, stable across the state changes reporting it.
636636
637 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
637 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
638638
639639 - `url: string`
640640
from line 646
646646
647647 The failure or cancellation detail, when known.
648648
649 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
649 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
650650
651651 - `is_error: optional boolean`
652652
from line 654
654654
655655 For a toolset member tool_result, the toolset family of the paired tool_use.
656656
657 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$
657 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]+$
658658
659659 - `ServerToolUseBlockParam object`
660660
from line 1032
10321032
10331033 - `tool_name: string`
10341034
1035 maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$
1035 minLength: 1, maxLength: 256, pattern: ^[a-zA-Z0-9_-]{1,256}$
10361036
10371037 - `cache_control: optional CacheControlEphemeral or null`
10381038
from line 1073
10731073
10741074 See [models](https://docs.anthropic.com/en/docs/models-overview) for additional details and options.
10751075
1076 - `string`
1077
10761078 - `"claude-fable-5-1" or "claude-opus-5-5" or "claude-mythos-5-1" or 15 more`
10771079
10781080 The model that will complete your prompt.
from line 1117
11151117
11161118 Powerful intelligence for long-running agents and coding
11171119
1118 - `"claude-mythos-preview"`
1119
1120 New class of intelligence, strongest in coding and cybersecurity
1121
11221120 - `"claude-opus-4-6"`
11231121
11241122 Powerful intelligence for long-running agents and coding
from line 1149
11511149
11521150 High-performance model for agents and coding
11531151
1154 - `string`
1152 - `"claude-mythos-preview"`
11551153
1154 **Deprecated**: Will reach end-of-life on June 30, 2026. Please migrate to claude-mythos-5. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
1155
1156 New class of intelligence, strongest in coding and cybersecurity
1157
11561158- `cache_control: optional CacheControlEphemeral or null`
11571159
11581160 Top-level cache control automatically applies a cache_control marker to the last cacheable block in the request.
from line 1189
11871189
11881190 Skill ID
11891191
1190 maxLength: 64, minLength: 1
1192 minLength: 1, maxLength: 64
11911193
11921194 - `version: optional string`
11931195
11941196 Skill version or 'latest' for most recent version
11951197
1196 maxLength: 64, minLength: 1
1198 minLength: 1, maxLength: 64
11971199
11981200 - `string`
11991201
12001202- `diagnostics: optional DiagnosticsParam or null`
12011203
1202 Request-level diagnostics. Currently carries the previous response
1203 id for prompt-cache divergence reporting.
1204 Request-level diagnostics. Supply `previous_message_id` to have the response include `diagnostics.cache_miss_reason` explaining any prompt-cache divergence from that prior request.
12041205
12051206 - `previous_message_id: optional string or null`
12061207
from line 1231
12301231
12311232 - `effort: optional "low" or "medium" or "high" or 2 more or null`
12321233
1233 All possible effort levels.
1234 How much effort the model should put into its response. Higher effort levels may result in more thorough analysis but take longer.
12341235
1236 Valid values are `low`, `medium`, `high`, `xhigh`, or `max`.
1237
12351238 - `"low"`
12361239
12371240 - `"medium"`
from line 1483
14801483
14811484 This is how the tool will be called by the model and in `tool_use` blocks.
14821485
1483 maxLength: 128, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,128}$
1486 minLength: 1, maxLength: 128, pattern: ^[a-zA-Z0-9_-]{1,128}$
14841487
14851488 - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"`
14861489
from line 1700
16971700
16981701 - `configs: optional BrowserToolsetConfigs or null`
16991702
1700 Per-member configuration for `browser_toolset_20260801`: one
1701 optional field per member tool, keyed by the member name — the same
1702 name the member's `tool_use` blocks carry. Every member is an
1703 accepted key, and a member's defaults apply wherever its key is
1704 absent. Unknown keys are rejected: the field set is this toolset
1705 version's complete member set.
1703 Sparse per-member overrides, keyed by member name. Absent, null, and {} are equivalent; a member's defaults apply wherever its key is absent.
17061704
17071705 - `type: optional BrowserTypeConfig or null`
17081706
from line 2127
21292127
21302128 - `configs: optional ComputerToolsetConfigs or null`
21312129
2132 Per-member configuration for `computer_toolset_20260801`: one
2133 optional field per member tool, keyed by the member name — the same
2134 name the member's `tool_use` blocks carry. Every member is an
2135 accepted key, and a member's defaults apply wherever its key is
2136 absent. Unknown keys are rejected: the field set is this toolset
2137 version's complete member set.
2130 Sparse per-member overrides, keyed by member name. Absent, null, and {} are equivalent; a member's defaults apply wherever its key is absent.
21382131
21392132 - `type: optional ComputerTypeConfig or null`
21402133
from line 2481
24882481
24892482 Maximum number of times the tool can be used in the API request.
24902483
2491 exclusiveMinimum: 0
2484 minimum: 1
24922485
24932486 - `strict: optional boolean`
24942487
from line 2497
25042497
25052498 The city of the user.
25062499
2507 maxLength: 255, minLength: 1
2500 minLength: 1, maxLength: 255
25082501
25092502 - `country: optional string or null`
25102503
25112504 The two letter [ISO country code](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2) of the user.
25122505
2513 maxLength: 2, minLength: 2
2506 minLength: 2, maxLength: 2
25142507
25152508 - `region: optional string or null`
25162509
25172510 The region of the user.
25182511
2519 maxLength: 255, minLength: 1
2512 minLength: 1, maxLength: 255
25202513
25212514 - `timezone: optional string or null`
25222515
25232516 The [IANA timezone](https://nodatime.org/TimeZones) of the user.
25242517
2525 maxLength: 255, minLength: 1
2518 minLength: 1, maxLength: 255
25262519
25272520 - `WebFetchTool20250910 object`
25282521
from line 2561
25682561
25692562 Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.
25702563
2571 exclusiveMinimum: 0
2564 minimum: 1
25722565
25732566 - `max_uses: optional number or null`
25742567
25752568 Maximum number of times the tool can be used in the API request.
25762569
2577 exclusiveMinimum: 0
2570 minimum: 1
25782571
25792572 - `strict: optional boolean`
25802573
from line 2575
25822575
25832576 - `url_sources: optional WebFetchURLSources or null`
25842577
2585 Which sources contribute to the set of URLs web fetch may fetch.
2578 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
25862579
2587 Each key is a tagged variant: `user_input` is `all` or `none`; the
2588 two tool filters are `all`, `none`, `only` (only the named tools'
2589 results) or `except` (every result but the named tools'). A named tool
2590 must be declared in this request's `tools[]`.
2591
25922580 - `client_tool_results: optional WebFetchURLSourceAll or WebFetchURLSourceNone or WebFetchURLSourceOnly or WebFetchURLSourceExcept`
25932581
25942582 Which client tools' results contribute fetchable URLs: "all", "none", or an only or except list of client tool names from tools[].
from line 2699
27112699
27122700 Maximum number of times the tool can be used in the API request.
27132701
2714 exclusiveMinimum: 0
2702 minimum: 1
27152703
27162704 - `strict: optional boolean`
27172705
from line 2753
27652753
27662754 Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.
27672755
2768 exclusiveMinimum: 0
2756 minimum: 1
27692757
27702758 - `max_uses: optional number or null`
27712759
27722760 Maximum number of times the tool can be used in the API request.
27732761
2774 exclusiveMinimum: 0
2762 minimum: 1
27752763
27762764 - `strict: optional boolean`
27772765
from line 2767
27792767
27802768 - `url_sources: optional WebFetchURLSources or null`
27812769
2782 Which sources contribute to the set of URLs web fetch may fetch.
2770 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
27832771
2784 Each key is a tagged variant: `user_input` is `all` or `none`; the
2785 two tool filters are `all`, `none`, `only` (only the named tools'
2786 results) or `except` (every result but the named tools'). A named tool
2787 must be declared in this request's `tools[]`.
2788
27892772 - `WebFetchTool20260309 object`
27902773
27912774 Web fetch tool with use_cache parameter for bypassing cached content.
from line 2815
28322815
28332816 Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.
28342817
2835 exclusiveMinimum: 0
2818 minimum: 1
28362819
28372820 - `max_uses: optional number or null`
28382821
28392822 Maximum number of times the tool can be used in the API request.
28402823
2841 exclusiveMinimum: 0
2824 minimum: 1
28422825
28432826 - `strict: optional boolean`
28442827
from line 2829
28462829
28472830 - `url_sources: optional WebFetchURLSources or null`
28482831
2849 Which sources contribute to the set of URLs web fetch may fetch.
2832 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
28502833
2851 Each key is a tagged variant: `user_input` is `all` or `none`; the
2852 two tool filters are `all`, `none`, `only` (only the named tools'
2853 results) or `except` (every result but the named tools'). A named tool
2854 must be declared in this request's `tools[]`.
2855
28562834 - `use_cache: optional boolean`
28572835
28582836 Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources.
from line 2875
28972875
28982876 Maximum number of times the tool can be used in the API request.
28992877
2900 exclusiveMinimum: 0
2878 minimum: 1
29012879
29022880 - `response_inclusion: optional "full" or "excluded"`
29032881
from line 2937
29592937
29602938 Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.
29612939
2962 exclusiveMinimum: 0
2940 minimum: 1
29632941
29642942 - `max_uses: optional number or null`
29652943
29662944 Maximum number of times the tool can be used in the API request.
29672945
2968 exclusiveMinimum: 0
2946 minimum: 1
29692947
29702948 - `response_inclusion: optional "full" or "excluded"`
29712949
from line 2959
29812959
29822960 - `url_sources: optional WebFetchURLSources or null`
29832961
2984 Which sources contribute to the set of URLs web fetch may fetch.
2962 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
29852963
2986 Each key is a tagged variant: `user_input` is `all` or `none`; the
2987 two tool filters are `all`, `none`, `only` (only the named tools'
2988 results) or `except` (every result but the named tools'). A named tool
2989 must be declared in this request's `tools[]`.
2990
29912964 - `use_cache: optional boolean`
29922965
29932966 Whether to use cached content. Set to false to bypass the cache and fetch fresh content. Only set to false when the user explicitly requests fresh content or when fetching rapidly-changing sources.
from line 3047
30743047
30753048 Note that even with `temperature` of `0.0`, the results will not be fully deterministic.
30763049
3077 maximum: 1, minimum: 0
3050 minimum: 0, maximum: 1
30783051
30793052- `top_k: optional number`
30803053
from line 3071
30983071
30993072 Recommended for advanced use cases only.
31003073
3101 maximum: 1, minimum: 0
3074 minimum: 0, maximum: 1
31023075
31033076## Returns
31043077
from line 3093
31203093
31213094 - `container: Container or null`
31223095
3123 Information about the container used in the request (for the code execution tool)
3096 Information about the container used in this request.
31243097
3098 This will be non-null if a container tool (e.g. code execution) was used.
3099
31253100 - `id: string`
31263101
31273102 Identifier for the container used in this request
from line 3123
31483123
31493124 Skill ID
31503125
3151 maxLength: 64, minLength: 1
3126 minLength: 1, maxLength: 64
31523127
31533128 - `version: string`
31543129
31553130 The resolved version: a skill version ID for custom skills.
31563131
3157 maxLength: 64, minLength: 1
3132 minLength: 1, maxLength: 64
31583133
31593134 - `content: array of ContentBlock`
31603135
from line 3302
33273302
33283303 - `text: string`
33293304
3330 minLength: 0
3331
33323305 - `ThinkingBlock object`
33333306
33343307 - `type: "thinking"`
from line 3382
34093382
34103383 For a toolset member tool_use, the toolset family.
34113384
3412 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$
3385 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]+$
34133386
34143387 - `ServerToolUseBlock object`
34153388
from line 3830
38573830
38583831 - `tool_name: string`
38593832
3860 maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$
3833 minLength: 1, maxLength: 256, pattern: ^[a-zA-Z0-9_-]{1,256}$
38613834
38623835 - `tool_use_id: string`
38633836
from line 3848
38753848
38763849 - `diagnostics: Diagnostics or null`
38773850
3878 Request-level diagnostics: why the prompt cache could not fully reuse
3879 the prefix of the request named by `diagnostics.previous_message_id`.
3851 Request-level diagnostics. `null` when the request did not supply `diagnostics`, or when it did and no prompt-cache divergence was detected.
38803852
38813853 - `cache_miss_reason: CacheMissReason or null`
38823854
from line 3912
39403912
39413913 See [models](https://docs.anthropic.com/en/docs/models-overview) for additional details and options.
39423914
3915 - `string`
3916
39433917 - `"claude-fable-5-1" or "claude-opus-5-5" or "claude-mythos-5-1" or 15 more`
39443918
39453919 The model that will complete your prompt.
from line 3956
39823956
39833957 Powerful intelligence for long-running agents and coding
39843958
3985 - `"claude-mythos-preview"`
3986
3987 New class of intelligence, strongest in coding and cybersecurity
3988
39893959 - `"claude-opus-4-6"`
39903960
39913961 Powerful intelligence for long-running agents and coding
from line 3988
40183988
40193989 High-performance model for agents and coding
40203990
4021 - `string`
3991 - `"claude-mythos-preview"`
40223992
3993 **Deprecated**: Will reach end-of-life on June 30, 2026. Please migrate to claude-mythos-5. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
3994
3995 New class of intelligence, strongest in coding and cybersecurity
3996
40233997 - `role: "assistant"`
40243998
40253999 Conversational role of the generated message.
from line 4004
40304004
40314005 - `stop_details: RefusalStopDetails or null`
40324006
4033 Structured information about a refusal.
4007 Structured information about why model output stopped.
40344008
4009 This is `null` when the `stop_reason` has no additional detail to report.
4010
40354011 - `type: "refusal"`
40364012
40374013 default: refusal
from line 4014
40384014
40394015 - `category: "cyber" or "bio" or "frontier_llm" or 2 more or null`
40404016
4041 The policy category that triggered a refusal.
4017 The policy category that triggered the refusal.
40424018
4019 `null` when the refusal doesn't map to a named category.
4020
40434021 - `"cyber"`
40444022
40454023 The request could enable cyber harm, such as malware or exploit development. Benign cybersecurity work can also trigger this category.
from line 4204
42264204
42274205 - `container: Container or null`
42284206
4229 Information about the container used in the request (for the code execution tool)
4207 Information about the container used in this request.
42304208
4209 This will be non-null if a container tool (e.g. code execution) was used.
4210
42314211 - `stop_details: RefusalStopDetails or null`
42324212
4233 Structured information about a refusal.
4213 Structured information about why model output stopped.
4214
4215 This is `null` when the `stop_reason` has no additional detail to report.
42344216
42354217 - `stop_reason: StopReason or null`
42364218
No line in this hunk matches that.