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

Annotations already signal read-only, idempotent, open-world, non-destructive behavior. The description goes well beyond this by revealing the output structure (version + schema_url + schema_hash + hosted_runtime facts), its equivalence to a well-known endpoint, and the intended verification workflow — actionable context the annotations and schema 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.

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

Two compact sentences with each clause earning its place: prerequisite, resource scope, standard equivalence, and usage workflow. Minor deduction for stylistic redundancy — 'Fetch' is used as an imperative in both sentences, and the '✅' decoration adds mild noise without semantic value.

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?

For a zero-parameter, read-only tool with an output schema, the description covers everything an agent needs: what is returned, how it maps to a known standard, how to validate it, and when to call it. No meaningful gap remains.

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 and schema description coverage is 100%, so the baseline is 4. The schema itself explains that the owner is derived from the authenticated principal, and the description adds the no-API-key prerequisite. Nothing more is needed.

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 concrete resource ('hash-verifiable AgentContractV1 descriptor' with version + schema_url + schema_hash, plus hosted_runtime facts). It further anchors meaning by noting the output is identical to /.well-known/agent.json, leaving no ambiguity about what the 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 explicit prerequisites ('No API key needed'), a timing directive ('call this now', 'before acting'), and a concrete consumption pattern (fetch schema_url, match schema_hash to validate). It lacks an explicit when-not-to-use or alternatives list, but with zero parameters and no sibling tools provided, the guidance is sufficient.

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