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 value beyond annotations by stating that no API key is needed, that the response is identical to /.well-known/agent.json, and that the schema_hash should be matched for validation. 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?

The description is compact and front-loads the most important guidance ('No API key needed — call this now'). The second sentence repeats 'fetch' but adds the validation workflow, so it earns its place. Slightly more could be trimmed, but it remains efficient.

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 full output schema, and annotations that cover side effects and idempotence, the description is complete: it tells the agent when to call, what it returns, how it maps to the standard agent.json, and how to use the hash for validation.

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 schema already fully documents the empty input and the authenticated-principal derivation. The description has nothing to add about parameters, so the baseline 4 applies.

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 operation: fetch the hash-verifiable AgentContractV1 descriptor with version, schema_url, and schema_hash, plus hosted_runtime facts, and equates it to /.well-known/agent.json. It is specific and readable, though it does not explicitly name verify_contract as the sibling for the separate verification step, so it stops just short of full sibling differentiation.

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?

No API key needed — call this now is an explicit when-to-use signal, and 'before acting' tells the agent to invoke this early. There are no exclusions or alternatives named, but for a zero-parameter discovery tool the usage context is clear enough.

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