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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds meaningful behavioral context beyond that: the response is hash-verifiable, identical to /.well-known/agent.json, and should be used to validate the platform contract. No contradictions 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?

Three sentences, each adding distinct value: call permission, returned content, and validation workflow. The emoji and 'call this now' phrase are slightly promotional, but overall the description is compact and well-structured.

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 tool with an output schema and strong annotations, the description is complete. It tells the agent what the response contains, how it maps to a known endpoint, and how to validate the contract before acting.

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 already documents that no arguments are needed and the owner is derived from the authenticated principal. With zero parameters, the description has no parameter burden to carry, so the baseline of 4 applies.

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 specific verb (fetch) and resource (hash-verifiable AgentContractV1 descriptor plus hosted_runtime facts), and anchors it to the familiar /.well-known/agent.json path. This clearly distinguishes what the tool returns and leaves no ambiguity about its purpose.

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?

It explicitly states no API key is needed, says to call it now, and instructs the agent to fetch schema_url and match schema_hash to validate the platform contract before acting. This gives a concrete when-to-use directive and a validation workflow, which is strong guidance for a zero-parameter read tool.

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