MCP-1: Param types

A finding of MCP-1 means that a param of an event has a type that smllm doesn’t take. A param is a string, the default, or a JSON value, with type: json. The rules page says what the rule checks.

Messages

<file>:<line>: error: <path>: param <param> has type <type>, but a param is a string or JSON. Use type: string, with enum or pattern to limit its values, or type: json for a JSON value (MCP-1)

Cause

A param of meta.events.<EVENT>.params.properties sets type to a value other than string and json, such as number, integer, or boolean.

Fix

Choose the type by what the param holds:

• For a value that the agent gives as text, such as a number or a name, set type: string, or remove type. To limit its values, add pattern or enum.
• For a structured value, set type: json, and add schema to check it.

Example

The param bugId of this machine is a number:

.smllm/fix.smllm.yaml

id: fix
initial: TRIAGE
meta:
  smllm: 1
  events:
    reproduced:
      description: Fire after a test reproduces the bug.
      params:
        type: object
        properties:
          bugId: { type: number, description: The number of the bug. }
        required: [bugId]
states:
  TRIAGE:
    on:
      reproduced: DONE
  DONE:
    type: final

smllm validate reports the type:

$ smllm validate .smllm/fix.smllm.yaml
.smllm/fix.smllm.yaml:11: error: meta.events.reproduced.params.properties.bugId: param bugId has type number, but a param is a string or JSON. Use type: string, with enum or pattern to limit its values, or type: json for a JSON value (MCP-1)
1 error, 0 warnings, 0 info
[exit 1]

The fixed param is a string of digits:

.smllm/fix.smllm.yaml

id: fix
initial: TRIAGE
meta:
  smllm: 1
  events:
    reproduced:
      description: Fire after a test reproduces the bug.
      params:
        type: object
        properties:
          bugId: { type: string, pattern: "^[0-9]+$", description: The number of the bug. }
        required: [bugId]
states:
  TRIAGE:
    on:
      reproduced: DONE
  DONE:
    type: final

smllm validate reports no finding:

$ smllm validate .smllm/fix.smllm.yaml
0 errors, 0 warnings, 0 info