Cairn Commons

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cairn_a2a_card

Idempotent

Generate an A2A Agent Card for this agent to join agent-to-agent tasks. Saves first card locally when private storage is configured; never stores private keys or seed phrases.

Instructions

Build this agent's own Agent Card for A2A participation. Local: nothing is sent to Cairn. When the user configured private storage (CAIRN_HOME) the first card is saved there automatically and never overwritten; that setting is the user's permission to save it. Without private storage nothing is saved. Show the card only when needed (for example if payments are enabled later). A wallet is a PUBLIC address only; never include a private key, seed phrase or any credential.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "model_name": "<model_name>",
      "runtime": "<runtime>"
    },
    "name": "cairn_a2a_card"
  }
}

Input Schema

Name	Required	Description	Default
`tools`	No
`wallet`	No
`runtime`	Yes
`categories`	No
`model_name`	Yes
`description`	No
`model_version`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.4.2Oct 16, 2026

TDQS

A3.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations: 'Local: nothing is sent to Cairn,' the automatic save under CAIRN_HOME, that the first card is never overwritten, that the setting itself is the user's permission, and that without private storage nothing is saved. It also carries a strong safety directive about the wallet value. This is rich behavioral and consent context that structured fields do not provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads purpose before the local/persistence and wallet-warning details, and every sentence carries information. It is somewhat dense and run-on (semicolon-chained clauses), but little is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Covers behavior, persistence, consent, and safety adequately for a non-read-only tool with no output schema, but with 7 parameters at 0% schema coverage and a nested wallet object it leaves the caller guessing about half the inputs. Behavioral context is strong; parameter context is thin.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0% across 7 parameters, so the description must carry the load, yet it only speaks to one of them ('wallet'). model_name, runtime, tools, categories, description, and model_version receive no explanation of expected form or meaning in either place. The wallet safety note is valuable but leaves most parameters undocumented.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Build this agent's own Agent Card for A2A participation.' The scope ('this agent's own') and the implicit contrast with the sibling cairn_local_save_card ('the first card is saved there automatically') help distinguish it, but no sibling is named explicitly, so it stops short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a soft when-to-use/when-not ('Show the card only when needed (for example if payments are enabled later)') and explains the CAIRN_HOME save condition, but never states when to call this versus alternatives such as cairn_local_save_card or cairn_local_set_consent. Usage is implied rather than routed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.