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

Annotations already mark the tool read-only, idempotent, and non-destructive, and the description adds real behavioral context: no auth required, exact source of truth (/.well-known/agent.json), hash-verifiability, and a validation workflow. No contradiction with annotations; remaining details such as failure modes are not disclosed, but the output schema covers return shape.

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 concise sentences with important information front-loaded ('No API key needed — call this now'). The final sentence adds a useful validation workflow rather than inflating length, so every sentence 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?

For a no-parameter read-only fetch with a rich annotation set and an output schema, the description is complete: it states when to call, that no auth is required, what fields are returned, and how the result should be used. Nothing needed for correct invocation is missing.

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 coverage is 100%, so the baseline is 4; the input schema already states that no arguments are needed and the owner is derived from the authenticated principal. The description adds no parameter-specific detail, which is acceptable because there is nothing to document.

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 concrete verb ('Fetch') and concrete resource ('hash-verifiable AgentContractV1 descriptor ... and hosted_runtime facts'), and further anchors it as identical to /.well-known/agent.json. It does not explicitly contrast with siblings like verify_contract or discover_agents, so it misses the top tier for 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?

The description gives clear situational context: no API key is needed, this should be called now, and the contract should be validated before acting. It does not state when not to use the tool or name alternatives, but the 'call this now / before acting' framing is enough to indicate timing and precedence.

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