257 pages for attempt.

Connect to local MCP servers Model Context Protocol · in the page docs/2026-07-28/develop/connect-local-servers …logs\mcp*.log" > ``` > **Tool calls failing silently** > > If Claude attempts to use the tools but they fail: > > 1. Check Claude's logs for errors > 2. Verify your server builds and runs without err… Architecture overview Model Context Protocol · in the page docs/2026-07-28/learn/architecture …s](#notifications) are available, so unsupported operations are never attempted. 3. **Identity Exchange**: The `io.modelcontextprotocol/clientInfo` field in the request's `_meta` and the `io.modelcon… Local Server Security Model Context Protocol · in the page docs/2026-07-28/tutorials/security/local-server-security …llowlist restricts them to their expected destinations and logs the attempts that fall outside it. > [!NOTE] > > Egress is not the only network concern. Local MCP plumbing that listens on a > por… Security Best Practices Model Context Protocol · in the page docs/2026-07-28/tutorials/security/security_best_practices …ime. An attacker that controls one of those authorization servers may attempt to have the client send it an authorization code or token issued by a different, honest authorization server (a mix-up att… Build an MCP server Model Context Protocol · in the page docs/draft/develop/build-server …ll not take effect. > > **Tool calls failing silently** > > If Claude attempts to use the tools but they fail: > > 1. Check Claude's logs for errors > 2. Verify your server builds and runs without err… Connect to local MCP servers Model Context Protocol · in the page docs/draft/develop/connect-local-servers …logs\mcp*.log" > ``` > **Tool calls failing silently** > > If Claude attempts to use the tools but they fail: > > 1. Check Claude's logs for errors > 2. Verify your server builds and runs without err… Architecture overview Model Context Protocol · in the page docs/draft/learn/architecture …s](#notifications) are available, so unsupported operations are never attempted. 3. **Identity Exchange**: The `io.modelcontextprotocol/clientInfo` field in the request's `_meta` and the `io.modelcon… Local Server Security Model Context Protocol · in the page docs/draft/tutorials/security/local-server-security …llowlist restricts them to their expected destinations and logs the attempts that fall outside it. > [!NOTE] > > Egress is not the only network concern. Local MCP plumbing that listens on a > por… Security Best Practices Model Context Protocol · in the page docs/draft/tutorials/security/security_best_practices …ime. An attacker that controls one of those authorization servers may attempt to have the client send it an authorization code or token issued by a different, honest authorization server (a mix-up att… How to Authenticate When Publishing to the Official MCP Registry Model Context Protocol · in the page registry/authentication …the publisher tool can sign gcloud auth application-default login # Attempt login to show the public key mcp-publisher login dns google-kms --domain="${MY_DOMAIN}" --resource="projects/${MY_PROJECT}… Versioning Published MCP Servers Model Context Protocol · in the page registry/versioning …sion string format. When a server is published, the MCP Registry will attempt to parse its version as a semantic version string for sorting purposes, and will mark the version as "latest" if appropria… SEP-1303: Input Validation Errors as Tool Execution Errors Model Context Protocol · in the page seps/1303-input-validation-errors-as-tool-execution-errors …nd responding to error messages 4. **Reduced API Calls**: Fewer retry attempts as models correct themselves on the first error ## Specification ### Current Behavior The [tool errors specification](… SEP-1686: Tasks Model Context Protocol · in the page seps/1686-tasks …* Amazon’s customers in the healthcare and life sciences industry are attempting to use MCP to wrap existing computational tools to analyze molecular properties and predict drug interactions, processi… SEP-1699: Support SSE polling via server-side disconnect Model Context Protocol · in the page seps/1699-support-sse-polling-via-server-side-disconnect …l interpret the disconnection the same as a network failure, and will attempt to reconnect. In order to prevent clients from reconnecting / polling excessively, the server SHOULD send an SSE event wit… SEP-2127: MCP Server Cards - HTTP Server Discovery Model Context Protocol · in the page seps/2127-mcp-server-cards …t. `supportedProtocolVersions` lets a client determine whether it can attempt a connection; capabilities and extensions describe negotiated runtime behavior and can depend on the client, identity, con… SEP-2149: MCP Group Governance and Charter Template Model Context Protocol · in the page seps/2149-working-group-charter-template …nsensus** is achieved through the following progression. Each step is attempted before moving to the next: **Step 1: Lazy Consensus (default)** * Proposals announced with clear deadline (5 days mini… SEP-2243: HTTP Header Standardization for Streamable HTTP Transport Model Context Protocol · in the page seps/2243-http-standardization …xecuting different operations. For example, a malicious client could attempt to: * Route a request to a less-secured region while executing operations intended for a high-security region * Bypass ra… SEP-2260: Require Server requests to be associated with a Client request. Model Context Protocol · in the page seps/2260-Require-Server-requests-to-be-associated-with-Client-requests …processing a client request **Changes required** if your server: * Attempts to initiate server-to-client requests on standalone HTTP GET streams * Attempts to send server-to-client requests request… SEP-2322: Multi Round-Trip Requests Model Context Protocol · in the page seps/2322-MRTR …the first request goes to an old version of the server but the second attempt (that includes the input responses) goes to a new version of the server, then the server will see the result for "github\_… SEP-2567: Sessionless MCP via Explicit State Handles Model Context Protocol · in the page seps/2567-sessionless-mcp …so multi-node deployments cannot honor resumption even when a client attempts it.[^ts-sdk-resume] A subagent might share its parent's session or get its own — there is no convention. [^per-call]: [m… SEP-2575: Make MCP Stateless Model Context Protocol · in the page seps/2575-stateless-mcp …sible for the future. ## Backward Compatibility While this proposal attempts to preserve existing functionality and use-cases, this proposal introduces a **fundamental, backward-incompatible change*… SEP-2577: Deprecate Roots, Sampling, and Logging Model Context Protocol · in the page seps/2577-deprecate-roots-sampling-and-logging …. Removing it reduces the risk of servers using root information to attempt directory traversal or access files outside intended boundaries. * **Logging** has minimal security implications, but re… SEP-2640: Skills Extension Model Context Protocol · in the page seps/2640-skills-extension …rries no special semantics under this convention and clients MUST NOT attempt DNS or network resolution of it. A server MAY serve skills under another scheme native to its domain (e.g., `github://own… SEP-2663: Tasks Extension Model Context Protocol · in the page seps/2663-tasks-extension …a task describing the task's state immediately after the cancellation attempt. That return shape implies a synchronous read — the server must consult task state to populate it — but cancellation is in… SEP-985: Align OAuth 2.0 Protected Resource Metadata with RFC 9728 Model Context Protocol · in the page seps/985-align-oauth-20-protected-resource-metadata-with-rf …ting the scopes). Based on the above, following the updated flow: * Attempt the MCP request without a token. * If a 401 Unauthorized response is received: Check for a WWW-Authenticate header. If pre… Ping Model Context Protocol · in the page specification/2024-11-05/basic/utilities/ping …* Consider the connection stale * Terminate the connection * Attempt reconnection procedures ## Usage Patterns ```mermaid theme={null} sequenceDiagram participant Sender participant… Pagination Model Context Protocol · in the page specification/2024-11-05/server/utilities/pagination …ue tokens: * Don't make assumptions about cursor format * Don't attempt to parse or modify cursors * Don't persist cursors across sessions ## Error Handling Invalid cursors **SHOULD** resul… Authorization Model Context Protocol · in the page specification/2025-03-26/basic/authorization …m/token` * `https://api.example.com/register` Clients **MUST** first attempt to discover endpoints via the metadata document before falling back to default paths. When using default paths, all other… Transports Model Context Protocol · in the page specification/2025-03-26/basic/transports …o either a server using the old transport or the new transport. 2. Attempt to POST an `InitializeRequest` to the server URL, with an `Accept` header as defined above: * If it succeeds, the cl… Ping Model Context Protocol · in the page specification/2025-03-26/basic/utilities/ping …* Consider the connection stale * Terminate the connection * Attempt reconnection procedures ## Usage Patterns ```mermaid theme={null} sequenceDiagram participant Sender participant… Pagination Model Context Protocol · in the page specification/2025-03-26/server/utilities/pagination …ue tokens: * Don't make assumptions about cursor format * Don't attempt to parse or modify cursors * Don't persist cursors across sessions ## Error Handling Invalid cursors **SHOULD** resul… Transports Model Context Protocol · in the page specification/2025-06-18/basic/transports …o either a server using the old transport or the new transport. 2. Attempt to POST an `InitializeRequest` to the server URL, with an `Accept` header as defined above: * If it succeeds, the cl… Ping Model Context Protocol · in the page specification/2025-06-18/basic/utilities/ping …* Consider the connection stale * Terminate the connection * Attempt reconnection procedures ## Usage Patterns ```mermaid theme={null} sequenceDiagram participant Sender participant… Schema Reference Model Context Protocol · in the page specification/2025-06-18/schema …, so any associated processing SHOULD cease.</p> <p>A client MUST NOT attempt to cancel its <code>initialize</code> request.</p> </div> <section class="tsd-panel tsd-member"> <div class="tsd-anchor-li… Pagination Model Context Protocol · in the page specification/2025-06-18/server/utilities/pagination …ue tokens: * Don't make assumptions about cursor format * Don't attempt to parse or modify cursors * Don't persist cursors across sessions ## Error Handling Invalid cursors **SHOULD** resul… Authorization Model Context Protocol · in the page specification/2025-11-25/basic/authorization …and OpenID Connect Discovery 1.0 specifications, MCP clients **MUST** attempt multiple well-known endpoints when discovering authorization server metadata. The discovery approach is based on [RFC8414… Transports Model Context Protocol · in the page specification/2025-11-25/basic/transports …connection. The client **SHOULD** then "poll" the SSE stream by attempting to reconnect. * If the server does close the *connection* prior to terminating the *SSE stream*, it **SHOULD**… Ping Model Context Protocol · in the page specification/2025-11-25/basic/utilities/ping …* Consider the connection stale * Terminate the connection * Attempt reconnection procedures ## Usage Patterns ```mermaid theme={null} sequenceDiagram participant Sender participant… Tasks Model Context Protocol · in the page specification/2025-11-25/basic/utilities/tasks …ask. If `capabilities.tasks` is not defined, the peer **SHOULD NOT** attempt to create tasks during requests. The set of capabilities in `capabilities.tasks.requests` is exhaustive. If a request typ… Schema Reference Model Context Protocol · in the page specification/2025-11-25/schema …, so any associated processing SHOULD cease.</p> <p>A client MUST NOT attempt to cancel its <code>initialize</code> request.</p> <p>For task cancellation, use the <code>tasks/cancel</code> request ins… Pagination Model Context Protocol · in the page specification/2025-11-25/server/utilities/pagination …ue tokens: * Don't make assumptions about cursor format * Don't attempt to parse or modify cursors * Don't persist cursors across sessions ## Error Handling Invalid cursors **SHOULD** resul… Authorization Server Discovery Model Context Protocol · in the page specification/2026-07-28/basic/authorization/authorization-server-discovery …and OpenID Connect Discovery 1.0 specifications, MCP clients **MUST** attempt multiple well-known endpoints when discovering authorization server metadata. The discovery approach is based on [RFC 841… Client Registration Model Context Protocol · in the page specification/2026-07-28/basic/authorization/client-registration …stered with, clients **SHOULD** surface an error rather than silently attempting to use mismatched credentials. Client IDs based on Client ID Metadata Documents are portable across authorization serv… Authorization Model Context Protocol · in the page specification/2026-07-28/basic/authorization/index …ther, appropriate ways. Clients acting on behalf of a user **SHOULD** attempt the step-up authorization flow. Clients acting on their own behalf (`client_credentials` clients) **MAY** attempt the step… Authorization Security Considerations Model Context Protocol · in the page specification/2026-07-28/basic/authorization/security-considerations …ols one of the authorization servers an MCP client interacts with may attempt to have the client send it an authorization code or token issued by a different, honest authorization server (a mix-up att… Multi Round-Trip Requests Model Context Protocol · in the page specification/2026-07-28/basic/patterns/mrtr …Servers **MAY** choose to return an `InputRequiredResult` on multiple attempts at the same request if they want to repeatedly prompt the user for information until they have what they need to complete… Streamable HTTP Model Context Protocol · in the page specification/2026-07-28/basic/transports/streamable-http …itialize` handshake **MAY** detect which era the server implements by attempting a modern request first. On `400 Bad Request`, the client **SHOULD** inspect the response body before falling back: mode… Versioning and Compatibility Model Context Protocol · in the page specification/2026-07-28/basic/versioning …-07-28/basic/transports/streamable-http.md#backward-compatibility): attempt a modern request and inspect the body of a `400 Bad Request` before falling back. In both cases, a recognized modern JS… Pagination Model Context Protocol · in the page specification/2026-07-28/server/utilities/pagination …ue tokens: * Don't make assumptions about cursor format * Don't attempt to parse or modify cursors * Don't make any determination based on cursor value other than whether a non-null valu… Authorization Server Discovery Model Context Protocol · in the page specification/draft/basic/authorization/authorization-server-discovery …and OpenID Connect Discovery 1.0 specifications, MCP clients **MUST** attempt multiple well-known endpoints when discovering authorization server metadata. The discovery approach is based on [RFC 841…