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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false; the description adds meaningful context beyond them: no API key is required, the output is identical to a standard well-known endpoint, and the returned hash enables verification. This gives the agent actionable safety and verification information 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 front-loaded with the most actionable fact ('No API key needed — call this now') and is compact at three sentences. The second and third sentences slightly overlap on 'Fetch schema_url' and 'match schema_hash', but the redundancy is minor and each sentence still contributes purpose or workflow guidance.

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 fetch tool with an output schema, the description covers everything an agent needs: authentication requirements, what is returned, endpoint equivalence, and how to use the data for contract validation. The output schema handles return-value documentation, so no essential information 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 the input schema already provides the baseline: 'No arguments — the owner is derived from the authenticated principal.' With 0 params, the description carries no burden to explain parameters, and the 100% schema description coverage confirms nothing is undocumented.

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.' The reference to 'identical to /.well-known/agent.json' further pins down what the tool returns. No sibling tools are listed, so sibling differentiation cannot be demonstrated, though the description is otherwise unambiguous.

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 line '✅ No API key needed — call this now' explicitly removes the main prerequisite and tells the agent this action is immediately safe to take. The description also prescribes when to use it: 'validate the platform contract before acting.' It does not name alternatives or exclusions, but the context is clear enough for a zero-parameter fetch tool.

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