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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is well covered. The description adds useful behavioral details beyond annotations: no API key required, the descriptor is hash-verifiable, and the content matches the standard well-known agent.json endpoint. There is 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 actionable facts: no API key needed and the call is safe to make now. The emoji and imperative call this now are minor noise, and the second sentence mixes usage instruction with tool behavior, but overall it remains efficient and scannable.

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, idempotent tool with an output schema and rich annotations, the description is complete. It explains what is returned, where the content is mirrored, whether credentials are needed, and how the result should be used before acting. No critical information is missing for an agent to invoke it 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?

The tool has zero parameters and the input schema has 100% description coverage, so the description is not expected to explain parameters. The schema already states that the owner is derived from the authenticated principal. The description adds no parameter semantics, but none are needed here.

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 action (Fetch) and the resource (hash-verifiable AgentContractV1 descriptor with version, schema_url, and schema_hash, plus hosted_runtime facts). It also identifies the descriptor as identical to /.well-known/agent.json. However, it slightly conflates fetching with validating, which could blur the line 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?

The description gives strong usage context: no API key is needed, the agent should call this now, and validation should happen before acting. It does not explicitly mention when not to use it or name verify_contract as the alternative for validation, but the timing and prerequisite guidance are clear enough.

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