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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, and the description adds meaningful context beyond them: no API key required, hash-verifiable descriptor, and equivalence to the well-known agent.json endpoint. This gives the agent safety and provenance expectations without contradicting 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 compact and front-loaded: the immediate 'No API key needed — call this now' signal is followed by a precise list of the fetched fields and a validation instruction. Every sentence carries actionable information with no filler.

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 and strong annotations, the description is complete. It tells the agent what data to expect (descriptor fields + hosted_runtime facts), where this data comes from, and how to validate the schema_hash 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 input schema fully documents this with 'No arguments — the owner is derived from the authenticated principal.' The description adds the auth-related context that no API key is needed, slightly reinforcing the parameter story. Baseline 4 for zero-parameter tools 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 clearly states the tool's function: fetch the hash-verifiable AgentContractV1 descriptor (version, schema_url, schema_hash) and hosted_runtime facts, equivalent to /.well-known/agent.json. It does not explicitly name or contrast sibling tools, so it stops short of full 5-level differentiation.

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 gives strong contextual guidance: 'No API key needed — call this now' and instructs to use it before acting to validate the platform contract. It does not mention explicit alternatives or when-not-to-use conditions, but the 'call this now' framing clearly positions it as the first read-only step.

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