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Fix Missing Required Client Capability error code (#15)

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The spec cites -32003 for "Missing Required Client Capability", but the
canonical code is -32021: SEP-2663 uses -32021 in all four of these
spots, the core 2026-07-28 schema defines MissingRequiredClientCapability
Error as -32021, and the TypeScript SDK exports
MISSING_REQUIRED_CLIENT_CAPABILITY = -32021. -32003 appears in no core
schema version.
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JoannaaKL 2026-08-20 04:21:20 +02:00 • committed by GitHub
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8
specification/draft/tasks.md
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@ -60,7 +60,7 @@ A server that has negotiated this extension **MAY** return `CreateTaskResult` in
A server **MUST NOT** return `CreateTaskResult` to a client that did not include the extension capability on its request, regardless of prior declarations. A client that has negotiated this extension **MUST** be prepared to handle either `CallToolResult` or `CreateTaskResult` in response to any supported request it issues. A client that receives `CreateTaskResult` in response to an unsupported request type **MUST** interpret this as an invalid response to the request.
If a server is unable to service a request to a client that does not declare this extension capability without returning `CreateTaskResult`, the server **MUST** return an error with the code `-32003` (Missing Required Client Capability), indicating the required extension in the error response:
If a server is unable to service a request to a client that does not declare this extension capability without returning `CreateTaskResult`, the server **MUST** return an error with the code `-32021` (Missing Required Client Capability), indicating the required extension in the error response:
```jsonl
{
@ -68,7 +68,7 @@ If a server is unable to service a request to a client that does not declare thi
"id": 1,
"error": {
// MISSING_REQUIRED_CLIENT_CAPABILITY
"code": -32003,
"code": -32021,
// Message provided for example purposes only. The content of this example message is non-normative.
"message": "Missing required client capability",
"data": {
@ -461,7 +461,7 @@ If a client requests task status notifications but does not declare the `io.mode
"jsonrpc": "2.0",
"id": 12,
"error": {
"code": -32003,
"code": -32021,
"message": "Missing required client capability",
"data": {
"requiredCapabilities": {
@ -794,7 +794,7 @@ Servers **MUST** return standard JSON-RPC errors for the following protocol erro
- Servers **MUST** return this error for `tasks/get`.
- Servers **SHOULD** return this error for `tasks/update` and `tasks/cancel`.
- Internal errors: `-32603` (Internal error)
- Missing required client capabilities: `-32003` (Missing Required Client Capability)
- Missing required client capabilities: `-32021` (Missing Required Client Capability)
- Servers **MUST** return this error for non-declaring clients requesting task notifications on `subscriptions/listen`.
- Servers **MUST** return this error for non-declaring clients issuing `tasks/get`, `tasks/update`, and `tasks/cancel` requests.