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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds valuable non-redundant context: no API key required, the payload is identical to /.well-known/agent.json, and the contract is hash-verifiable. No contradiction with annotations.

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, front-loaded with the most actionable information ('No API key needed — call this now'), followed by the return content and validation purpose. No redundant filler; every sentence contributes meaning.

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 metadata fetch with an output schema present, the description is complete: it states purpose, auth requirements, the contract identity, and how to use the returned hash/schema_url pair. The output schema covers any return-format details not spelled out.

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 schema already fully captures the input surface. The schema description adds that the owner is derived from the authenticated principal, which is the only meaningful parameter-related information. Baseline 4 is appropriate for a parameterless tool.

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 clearly states the verb ('Fetch') and a specific resource ('hash-verifiable AgentContractV1 descriptor' with version, schema_url, schema_hash, hosted_runtime facts), and equates it to /.well-known/agent.json. It does not explicitly differentiate from the sibling verify_contract, which is a related but distinct action, so it falls slightly 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.

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

The description gives clear context: no API key is needed, and the agent is told to 'call this now,' implying it is a safe first step before acting. It does not explicitly discuss alternatives or when not to use it, but the guidance is strong enough for a zero-parameter read-only call.

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