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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world. Beyond that, the description adds that handshake outcomes include auth_required, unreachable, tool count, and tool-list drift, which tells the agent what failure modes and states it will observe. It doesn't mention rate limits or freshness semantics, keeping it at 4.

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, front-loaded with the core purpose followed immediately by the actionable guidance. Every clause earns its place, and the parenthetical efficiently enumerates status types.

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 one-parameter read-only lookup with no output schema, the description covers what it returns (status enum, tool counts, drift) and when to use it. It's nearly complete; a minor gap is that it doesn't explicitly say what happens if the domain isn't found, though 'unreachable' partially covers that.

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?

Schema coverage is 100% and the single parameter has a clear description ('Bare domain or host, e.g. example.com'). The tool description doesn't need to add more, but it implicitly frames 'domain' as the selection key for which MCP servers to inspect, which is slightly additive.

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?

States a specific verb and resource: it lists which remote MCP servers the official registry lists on a domain and reports what each endpoint answered during handshake testing. The parenthetical enumerates the exact result fields, so the agent knows precisely what this 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?

'Use before selecting an MCP tool from that domain' gives a clear when-to-use trigger. However, it doesn't name an alternative sibling like registry_lookup or list_verified_capabilities, so there's no explicit differentiation or when-not statement.

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