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

Annotations already cover readOnly, idempotent, and non-destructive hints, so the bar for description value-add is met by the extra context: no API key requirement, hash-verifiable descriptor, equivalence to /.well-known/agent.json, and the schema_hash validation workflow. These details explain the trust model and how the output should be used, going beyond what the annotations state. 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?

Two sentences with the call-to-action front-loaded and the key output content packed into the first sentence. It is compact and scannable, though the second sentence partially restates 'schema_url' and 'schema_hash' already listed in the first, and the emoji is mildly gimmicky.

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 contract-fetching tool, the description covers what is returned, the validation workflow, and authentication requirements. Since the tool has an output schema, return-value details are covered by that schema. It is a complete enough definition, missing only an explicit 'when not to use' boundary, which is minor given the tool's simplicity.

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 schema description covers 100% of them, so there is nothing for the description to add. The schema itself already clarifies that 'the owner is derived from the authenticated principal,' and the description correctly focuses on output and usage rather than inputs. Baseline 4 for a zero-parameter tool is appropriate.

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 states a specific verb and resource: 'Fetch the hash-verifiable AgentContractV1 descriptor (version + schema_url + schema_hash) and the hosted_runtime facts.' It further clarifies the resource by equating it to '/.well-known/agent.json', which leaves no ambiguity about what the tool returns. This clearly distinguishes it from any contract-retrieval alternative.

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 opening instruction 'No API key needed — call this now' tells the agent this is the go-to, unauthenticated way to retrieve the platform contract, giving a clear when-to-use signal. The second sentence adds a concrete workflow: 'Fetch schema_url and match schema_hash to validate the platform contract before acting.' However, with no sibling tools listed, it doesn't state when not to use this tool or name alternatives.

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