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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=true, and destructveHint=false. The description adds meaningful context beyond those flags: no API key/auth requirement, the payload contents, and the hash-verification workflow. It does not contradict the annotations — 'Fetch' matches the read-only hint.

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 short sentences, each carrying information: auth note, resource + contents, and usage purpose. The 'call this now' phrasing and emoji are slightly chatty/pushy, but not bloat — they convey the no-prerequisite entry point. Reasonably front-loaded.

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?

The tool is simple (zero params) and the output schema handles return-value structure, so the description is complete for invocation purposes. It covers what the payload contains, how to verify it (match schema_hash), and the auth model. An agent can confidently call this without additional research.

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?

With zero parameters, the schema fully covers the input surface (coverage 100%). The schema description notes the owner derives from the authenticated principal, and the tool description adds no conflicting parameter details. The baseline 4 for 0-parameter tools 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 uses a specific verb ('Fetch') with a specific resource ('the hash-verifiable AgentContractV1 descriptor') and enumerates its contents (version, schema_url, schema_hash, hosted_runtime facts). It also anchors the meaning by explicitly equating it to the standard /.well-known/agent.json endpoint, which leaves no ambiguity about what the tool returns.

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 clear when-to-use context: fetch this contract and validate schema_hash before acting, with a note that no API key is needed. It does not explicitly name alternatives or state when not to use it, but for a zero-parameter read-only utility the guidance is sufficient.

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