Create a Message Batch changedapi/messages/batches/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+125added
Lines−152removed
From line
31
where the diff opens
First seen
14 Aug 2026
this site's first read of the page
Recorded edits12to this page, all time
The whole hunk
from line 31, old and new numbered
/
from line 31
3131
3232 List of requests for prompt completion. Each is an individual request to create a Message.
3333
34 maxItems: 100000, minItems: 1
34 minItems: 1, maxItems: 100000
3535
3636 - `custom_id: string`
3737
from line 39
3939
4040 Must be unique for each request within the Message Batch.
4141
42 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,64}$
42 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]{1,64}$
4343
4444 - `params: object`
4545
from line 159
159159
160160 - `document_title: string or null`
161161
162 maxLength: 500, minLength: 1
162 minLength: 1, maxLength: 500
163163
164164 - `end_char_index: number`
165165
from line 179
179179
180180 - `document_title: string or null`
181181
182 maxLength: 500, minLength: 1
182 minLength: 1, maxLength: 500
183183
184184 - `end_page_number: number`
185185
from line 203
203203
204204 - `document_title: string or null`
205205
206 maxLength: 500, minLength: 1
206 minLength: 1, maxLength: 500
207207
208208 - `end_block_index: number`
209209
from line 227
227227
228228 - `title: string or null`
229229
230 maxLength: 512, minLength: 1
230 minLength: 1, maxLength: 512
231231
232232 - `url: string`
233233
from line 383
383383
384384 - `title: optional string or null`
385385
386 maxLength: 500, minLength: 1
386 minLength: 1, maxLength: 500
387387
388388 - `SearchResultBlockParam object`
389389
from line 447
447447
448448 - `name: string`
449449
450 maxLength: 200, minLength: 1
450 minLength: 1, maxLength: 200
451451
452452 - `cache_control: optional CacheControlEphemeral or null`
453453
from line 483
483483
484484 For a toolset member tool_use, the toolset family this member belongs to.
485485
486 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$
486 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]+$
487487
488488 - `ToolResultBlockParam object`
489489
from line 519
519519
520520 - `tool_name: string`
521521
522 maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$
522 minLength: 1, maxLength: 256, pattern: ^[a-zA-Z0-9_-]{1,256}$
523523
524524 - `cache_control: optional CacheControlEphemeral or null`
525525
from line 547
547547
548548 The caller-assigned identifier for this tab, unique within the inventory.
549549
550 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
550 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
551551
552552 - `title: string`
553553
from line 573
573573
574574 Tabs opened and download state changes during this call. "Nothing to report" is expressed by omitting the field, never by an empty list.
575575
576 maxItems: 200, minItems: 1
576 minItems: 1, maxItems: 200
577577
578578 - `BrowserStateChangeTabOpened object`
579579
from line 591
591591
592592 The `tab_id` of the opened tab, present in `tabs`.
593593
594 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
594 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
595595
596596 - `BrowserStateChangeDownloadStarted object`
597597
from line 603
603603
604604 The caller-assigned identifier for this download, stable across the state changes reporting it.
605605
606 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
606 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
607607
608608 - `url: string`
609609
from line 624
624624
625625 The caller-assigned identifier for this download, stable across the state changes reporting it.
626626
627 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
627 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
628628
629629 - `url: string`
630630
from line 636
636636
637637 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.
638638
639 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
639 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
640640
641641 - `size_bytes: optional number or null`
642642
from line 654
654654
655655 The caller-assigned identifier for this download, stable across the state changes reporting it.
656656
657 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
657 minLength: 1, maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
658658
659659 - `url: string`
660660
from line 666
666666
667667 The failure or cancellation detail, when known.
668668
669 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
669 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
670670
671671 - `is_error: optional boolean`
672672
from line 674
674674
675675 For a toolset member tool_result, the toolset family of the paired tool_use.
676676
677 maxLength: 64, minLength: 1, pattern: ^[a-zA-Z0-9_-]+$
677 minLength: 1, maxLength: 64, pattern: ^[a-zA-Z0-9_-]+$
678678
679679 - `ServerToolUseBlockParam object`
680680
from line 1052
10521052
10531053 - `tool_name: string`
10541054
1055 maxLength: 256, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,256}$
1055 minLength: 1, maxLength: 256, pattern: ^[a-zA-Z0-9_-]{1,256}$
10561056
10571057 - `cache_control: optional CacheControlEphemeral or null`
10581058
from line 1093
10931093
10941094 See [models](https://docs.anthropic.com/en/docs/models-overview) for additional details and options.
10951095
1096 - `string`
1097
10961098 - `"claude-fable-5-1" or "claude-opus-5-5" or "claude-mythos-5-1" or 15 more`
10971099
10981100 The model that will complete your prompt.
from line 1137
11351137
11361138 Powerful intelligence for long-running agents and coding
11371139
1138 - `"claude-mythos-preview"`
1139
1140 New class of intelligence, strongest in coding and cybersecurity
1141
11421140 - `"claude-opus-4-6"`
11431141
11441142 Powerful intelligence for long-running agents and coding
from line 1169
11711169
11721170 High-performance model for agents and coding
11731171
1174 - `string`
1172 - `"claude-mythos-preview"`
11751173
1174 **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.
1175
1176 New class of intelligence, strongest in coding and cybersecurity
1177
11761178 - `cache_control: optional CacheControlEphemeral or null`
11771179
11781180 Top-level cache control automatically applies a cache_control marker to the last cacheable block in the request.
from line 1209
12071209
12081210 Skill ID
12091211
1210 maxLength: 64, minLength: 1
1212 minLength: 1, maxLength: 64
12111213
12121214 - `version: optional string`
12131215
12141216 Skill version or 'latest' for most recent version
12151217
1216 maxLength: 64, minLength: 1
1218 minLength: 1, maxLength: 64
12171219
12181220 - `string`
12191221
12201222 - `diagnostics: optional DiagnosticsParam or null`
12211223
1222 Request-level diagnostics. Currently carries the previous response
1223 id for prompt-cache divergence reporting.
1224 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.
12241225
12251226 - `previous_message_id: optional string or null`
12261227
from line 1251
12501251
12511252 - `effort: optional "low" or "medium" or "high" or 2 more or null`
12521253
1253 All possible effort levels.
1254 How much effort the model should put into its response. Higher effort levels may result in more thorough analysis but take longer.
12541255
1256 Valid values are `low`, `medium`, `high`, `xhigh`, or `max`.
1257
12551258 - `"low"`
12561259
12571260 - `"medium"`
from line 1503
15001503
15011504 This is how the tool will be called by the model and in `tool_use` blocks.
15021505
1503 maxLength: 128, minLength: 1, pattern: ^[a-zA-Z0-9_-]{1,128}$
1506 minLength: 1, maxLength: 128, pattern: ^[a-zA-Z0-9_-]{1,128}$
15041507
15051508 - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"`
15061509
from line 1720
17171720
17181721 - `configs: optional BrowserToolsetConfigs or null`
17191722
1720 Per-member configuration for `browser_toolset_20260801`: one
1721 optional field per member tool, keyed by the member name — the same
1722 name the member's `tool_use` blocks carry. Every member is an
1723 accepted key, and a member's defaults apply wherever its key is
1724 absent. Unknown keys are rejected: the field set is this toolset
1725 version's complete member set.
1723 Sparse per-member overrides, keyed by member name. Absent, null, and {} are equivalent; a member's defaults apply wherever its key is absent.
17261724
17271725 - `type: optional BrowserTypeConfig or null`
17281726
from line 2147
21492147
21502148 - `configs: optional ComputerToolsetConfigs or null`
21512149
2152 Per-member configuration for `computer_toolset_20260801`: one
2153 optional field per member tool, keyed by the member name — the same
2154 name the member's `tool_use` blocks carry. Every member is an
2155 accepted key, and a member's defaults apply wherever its key is
2156 absent. Unknown keys are rejected: the field set is this toolset
2157 version's complete member set.
2150 Sparse per-member overrides, keyed by member name. Absent, null, and {} are equivalent; a member's defaults apply wherever its key is absent.
21582151
21592152 - `type: optional ComputerTypeConfig or null`
21602153
from line 2501
25082501
25092502 Maximum number of times the tool can be used in the API request.
25102503
2511 exclusiveMinimum: 0
2504 minimum: 1
25122505
25132506 - `strict: optional boolean`
25142507
from line 2517
25242517
25252518 The city of the user.
25262519
2527 maxLength: 255, minLength: 1
2520 minLength: 1, maxLength: 255
25282521
25292522 - `country: optional string or null`
25302523
25312524 The two letter [ISO country code](https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2) of the user.
25322525
2533 maxLength: 2, minLength: 2
2526 minLength: 2, maxLength: 2
25342527
25352528 - `region: optional string or null`
25362529
25372530 The region of the user.
25382531
2539 maxLength: 255, minLength: 1
2532 minLength: 1, maxLength: 255
25402533
25412534 - `timezone: optional string or null`
25422535
25432536 The [IANA timezone](https://nodatime.org/TimeZones) of the user.
25442537
2545 maxLength: 255, minLength: 1
2538 minLength: 1, maxLength: 255
25462539
25472540 - `WebFetchTool20250910 object`
25482541
from line 2581
25882581
25892582 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.
25902583
2591 exclusiveMinimum: 0
2584 minimum: 1
25922585
25932586 - `max_uses: optional number or null`
25942587
25952588 Maximum number of times the tool can be used in the API request.
25962589
2597 exclusiveMinimum: 0
2590 minimum: 1
25982591
25992592 - `strict: optional boolean`
26002593
from line 2595
26022595
26032596 - `url_sources: optional WebFetchURLSources or null`
26042597
2605 Which sources contribute to the set of URLs web fetch may fetch.
2598 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
26062599
2607 Each key is a tagged variant: `user_input` is `all` or `none`; the
2608 two tool filters are `all`, `none`, `only` (only the named tools'
2609 results) or `except` (every result but the named tools'). A named tool
2610 must be declared in this request's `tools[]`.
2611
26122600 - `client_tool_results: optional WebFetchURLSourceAll or WebFetchURLSourceNone or WebFetchURLSourceOnly or WebFetchURLSourceExcept`
26132601
26142602 Which client tools' results contribute fetchable URLs: "all", "none", or an only or except list of client tool names from tools[].
from line 2719
27312719
27322720 Maximum number of times the tool can be used in the API request.
27332721
2734 exclusiveMinimum: 0
2722 minimum: 1
27352723
27362724 - `strict: optional boolean`
27372725
from line 2773
27852773
27862774 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.
27872775
2788 exclusiveMinimum: 0
2776 minimum: 1
27892777
27902778 - `max_uses: optional number or null`
27912779
27922780 Maximum number of times the tool can be used in the API request.
27932781
2794 exclusiveMinimum: 0
2782 minimum: 1
27952783
27962784 - `strict: optional boolean`
27972785
from line 2787
27992787
28002788 - `url_sources: optional WebFetchURLSources or null`
28012789
2802 Which sources contribute to the set of URLs web fetch may fetch.
2790 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
28032791
2804 Each key is a tagged variant: `user_input` is `all` or `none`; the
2805 two tool filters are `all`, `none`, `only` (only the named tools'
2806 results) or `except` (every result but the named tools'). A named tool
2807 must be declared in this request's `tools[]`.
2808
28092792 - `WebFetchTool20260309 object`
28102793
28112794 Web fetch tool with use_cache parameter for bypassing cached content.
from line 2835
28522835
28532836 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.
28542837
2855 exclusiveMinimum: 0
2838 minimum: 1
28562839
28572840 - `max_uses: optional number or null`
28582841
28592842 Maximum number of times the tool can be used in the API request.
28602843
2861 exclusiveMinimum: 0
2844 minimum: 1
28622845
28632846 - `strict: optional boolean`
28642847
from line 2849
28662849
28672850 - `url_sources: optional WebFetchURLSources or null`
28682851
2869 Which sources contribute to the set of URLs web fetch may fetch.
2852 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
28702853
2871 Each key is a tagged variant: `user_input` is `all` or `none`; the
2872 two tool filters are `all`, `none`, `only` (only the named tools'
2873 results) or `except` (every result but the named tools'). A named tool
2874 must be declared in this request's `tools[]`.
2875
28762854 - `use_cache: optional boolean`
28772855
28782856 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 2895
29172895
29182896 Maximum number of times the tool can be used in the API request.
29192897
2920 exclusiveMinimum: 0
2898 minimum: 1
29212899
29222900 - `response_inclusion: optional "full" or "excluded"`
29232901
from line 2957
29792957
29802958 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.
29812959
2982 exclusiveMinimum: 0
2960 minimum: 1
29832961
29842962 - `max_uses: optional number or null`
29852963
29862964 Maximum number of times the tool can be used in the API request.
29872965
2988 exclusiveMinimum: 0
2966 minimum: 1
29892967
29902968 - `response_inclusion: optional "full" or "excluded"`
29912969
from line 2979
30012979
30022980 - `url_sources: optional WebFetchURLSources or null`
30032981
3004 Which sources contribute to the set of URLs web fetch may fetch.
2982 Which sources contribute to the set of URLs the tool may fetch. Omitted means every source.
30052983
3006 Each key is a tagged variant: `user_input` is `all` or `none`; the
3007 two tool filters are `all`, `none`, `only` (only the named tools'
3008 results) or `except` (every result but the named tools'). A named tool
3009 must be declared in this request's `tools[]`.
3010
30112984 - `use_cache: optional boolean`
30122985
30132986 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 3067
30943067
30953068 Note that even with `temperature` of `0.0`, the results will not be fully deterministic.
30963069
3097 maximum: 1, minimum: 0
3070 minimum: 0, maximum: 1
30983071
30993072 - `top_k: optional number`
31003073
from line 3091
31183091
31193092 Recommended for advanced use cases only.
31203093
3121 maximum: 1, minimum: 0
3094 minimum: 0, maximum: 1
31223095
31233096## Returns
31243097
No line in this hunk matches that.