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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond the annotations: no API key is required, the returned descriptor is hash-verifiable, and the result is identical to /.well-known/agent.json. It also tells the agent to fetch schema_url and match schema_hash to validate the contract, which explains what to do with the data.

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 two sentences with no wasted words. The most decisive signal ('No API key needed — call this now') is front-loaded, followed by exactly what is fetched and how to use it. 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 zero-parameter, read-only, idempotent tool with an output schema, this description is complete. It covers what the tool returns, the authentication requirement, the well-known endpoint equivalence, and the follow-up validation action. Nothing essential is missing for an agent to select and invoke the tool 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, so the baseline is 4. The schema already documents that no arguments are needed and that the owner is derived from the authenticated principal. The description reinforces this by saying 'call this now' with no parameter setup, which is consistent and sufficient for a parameterless tool.

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 identifies a specific verb and resource: 'Fetch the hash-verifiable AgentContractV1 descriptor (version + schema_url + schema_hash) and the hosted_runtime facts.' It also states the output is identical to /.well-known/agent.json, which gives the agent a precise mental model of what this tool returns. It does not explicitly name a sibling alternative, but the resource is specific enough to avoid confusion with the listed siblings.

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 provides clear usage context: 'call this now,' 'No API key needed,' and 'validate the platform contract before acting.' This tells the agent when and why to invoke the tool. It does not explicitly describe when not to use it or name alternative tools, but for a zero-parameter read-only contract fetcher the timing guidance is sufficient.

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