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

Annotations already declare readOnly/openWorld/idempotent safety, and the description adds valuable non-obvious context: no API key is required, the content is hash-verifiable, and it is identical to the standard agent.json endpoint. It also explains the validation workflow (fetch schema_url, match schema_hash), going well beyond the structured hints.

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 deliver the key facts efficiently, front-loaded with the most actionable detail (no API key needed). The 'call this now' phrasing is slightly promotional and redundant, but the overall length is appropriate and dense with meaningful information.

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, the description is complete: it states what is fetched, how it maps to a known standard, how to use it for validation, and the auth requirement. There are no meaningful gaps an agent would need filled.

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 per the baseline the description carries no requirement to explain arguments. The input schema itself already states 'No arguments — the owner is derived from the authenticated principal,' so nothing is missing.

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 uses a specific verb ('Fetch') with a clearly named resource (hash-verifiable AgentContractV1 descriptor: version + schema_url + schema_hash) and the hosted_runtime facts. It also anchors the behavior by equating it to a well-known standard (/.well-known/agent.json), leaving no ambiguity about what is returned.

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 explicitly directs the agent to call this tool first ('call this now') and explains when it should be used ('validate the platform contract before acting'). It does not name alternatives, but no sibling tools are present in this context, so explicit exclusions are not needed.

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