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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false. The description adds meaningful context beyond annotations: no API key is needed, the payload is hash-verifiable, and the output matches a known standard (agent.json). This reassures an agent that the call is safe and self-contained.

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

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

Three short sentences, each earning its place: auth requirement, response contents, and intended validation workflow. There is no filler or redundancy; the front-loaded imperative is purposeful and actionable.

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

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

Given an empty input schema and an existing output schema, the description fully covers when to call it, what it returns, and how to use the returned values (match schema_hash and validate before acting). It also ties the output to the standard agent.json contract, making the tool's role complete.

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

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

There are zero parameters, so the description has no parameter burden. The schema already explains that owner derivation comes from the authenticated principal, and with 100% schema description coverage, the baseline 4 per rubric is appropriate.

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

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

The description names a specific verb ('Fetch') and a specific resource (hash-verifiable AgentContractV1 descriptor) with enumerated fields (version + schema_url + schema_hash) plus hosted_runtime facts. It also clarifies the output is identical to /.well-known/agent.json, removing ambiguity about what this tool returns.

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

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

The description gives clear context: call this before acting ('call this now', 'validate the platform contract before acting') and notes no API key is needed. However, it does not explicitly name alternative tools or conditions when not to use it, so it falls just short of the top score.

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