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

The annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds useful behavioral facts beyond annotations: no API key is required, the response is identical to /.well-known/agent.json, and the returned hash fields are intended for validation. This adds meaningful context without contradicting the 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?

The description is compact and front-loaded, with the key action stated in the first sentence. The encouraging phrase 'call this now' is slightly promotional and not necessary, but overall every substantive instruction earns its place.

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 zero parameters, a provided output schema, and annotations that fully cover the safety profile, the description supplies the missing operational context: an alternate well-known URL representation, the returned fields, and the validation purpose. This is sufficient for an agent to call and use the tool correctly.

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?

With zero parameters and 100% schema coverage, the schema fully documentes that no arguments are needed. The description adds slightly by noting the owner is derived from the authenticated principal (already in the schema), so there is no parameter ambiguity to resolve.

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 ('AgentContractV1 descriptor' with version + schema_url + schema_hash) and hosted_runtime facts, and equates it with /.well-known/agent.json. This clearly identifies what the tool does, though it does not explicitly contrast it with the sibling verify_contract tool.

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?

It explicitly says 'No API key needed — call this now' and instructs the agent to validate the platform contract 'before acting.' This provides clear usage context. However, it does not say when NOT to use this tool or name an alternative such as verify_contract.

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