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mcp client

mcp client

The mcp client binding forwards outbound MCP requests to an upstream MCP server.

mcp_client:
  type: mcp
  kind: client
  options:
    server: https://upstream.example.com/mcp
  exit: sys:http_client

Configuration (* required)

options*

object

The client kind mcp specific options.

options:
  server: https://upstream.example.com/mcp

options.server*

string | Pattern: ^https?://

URL of the upstream MCP server to forward requests to.

options.authorization

object as map of named object properties

Authorization by a named guard, used to authorize outbound requests to the upstream MCP server.

authorization:
  my_jwt_guard:
    credentials: "Bearer {credentials}"

authorization.credentials

string | Default: Bearer {credentials}

Template used to build the outbound Authorization header. When it contains the {credentials} placeholder, the placeholder is replaced with the value returned by the named guard. When omitted from the template, the header is sent as the literal template value regardless of the guard outcome.

routes

array of object

Conditional mcp specific routes, resolved per matched tool, prompt, or resource, used to authorize individual tools/call, prompts/get, and resources/read requests against the upstream MCP server.

routes:
  - exit: sys:http_client
    when:
      - tool:
          - get_weather
  - exit: sys:http_client
    when:
      - tool:
          - get_status
    guarded:
      my_jwt_guard:
        - read

routes[].guarded

object as map of named array of string

Roles required by the named guard. When a guarded route matches a requested tool, prompt, or resource, the session must be authorized for the listed roles, otherwise the request is rejected. Also drives which entries are stamped with securitySchemes in tools/list responses.

routes:
  - guarded:
      my_jwt_guard:
        - read

routes[].when

array of object

List of conditions (any match) to match this route. Read more: When a route matches

when[].tool

string, array of string

Glob patterns of tool names to match, where * matches any sequence of characters. A bare string is shorthand for a single-element array. When omitted, all tools are admitted.

when[].prompt

string, array of string

Glob patterns of prompt names to match, where * matches any sequence of characters. A bare string is shorthand for a single-element array. When omitted, all prompts are admitted.

when[].resource

string, array of string

Glob patterns of resource URIs to match, where * matches any sequence of characters. A bare string is shorthand for a single-element array. When omitted, all resources are admitted.

routes[].with

object

Reserved for a future per-route override. Currently has no effect: a matched request is always forwarded unmodified.

routes[].exit

string

Next binding when following this route. At least one route must declare its own exit unless the binding declares a top-level exit.

exit

string

Default exit binding when no conditional routes are viable. Required unless every route declares its own exit.

exit: sys:http_client

telemetry

object

Defines the desired telemetry for the binding.

telemetry.metrics

array

Telemetry metrics to track

telemetry:
  metrics:
    - stream.*

telemetry.attributes

object as map of named string properties

Telemetry attributes to add to the binding metrics.

Gateway Version