MCP servers

Required

• Check the caller's rights on every handle

  AGT-12

  A handle that one tool returns and another accepts names data, it does not grant access. Check on every call that the caller's token may use it.

• Reject MCP requests whose headers disagree with the body

  AGT-14

  Require MCP-Protocol-Version, Mcp-Method and, on tool calls, resource reads and prompt requests, Mcp-Name. Refuse any request whose headers differ from its JSON body.

Recommended

• Build the MCP server without sessions

  AGT-11

  Answer every MCP request from that request alone. Read the protocol version and client capabilities from its _meta, and keep state across calls only behind handles passed as tool arguments.

• Register MCP clients with Client ID Metadata Documents

  AGT-13

  Let MCP clients you have never met use an HTTPS address as their client ID. Fetch the metadata document there and check it, instead of open dynamic registration.

• Keep the tool list within a token budget

  AGT-15

  Set a token budget for the whole tools/list answer and fail the build when it grows past it. Each tool's description says when to use it and when not to.

• Report bad arguments as tool results instead of protocol errors

  AGT-16

  Return bad arguments, missing records and business rule failures as a tool result with isError: true. Keep JSON-RPC errors for unknown tools, malformed requests and server faults.

• Send cache hints and a stable order with every list

  AGT-17

  Return list results in the same order while the set is unchanged. Give each cacheable result a ttlMs, and a cacheScope of private whenever it depends on who asks.

• Sign the state you hand back for a second round

  AGT-18

  When a tool needs more input, return an input_required result. Sign any requestState you include, and check the signature on the retry.

Optional

• Run long work as tasks

  AGT-19

  When a tool call takes longer than 30 seconds, return a task handle through the MCP Tasks extension. Return it only to clients that declared the extension.