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

Beyond the annotations (openWorldHint, non-readOnly, non-destructive), the description discloses key behavioral traits: invoke runs without installing, may return connect or checkout links requiring user action and retry, writes need owner/admin, and search/describe flag installation status. This adds context the annotations don't provide and contradicts nothing.

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 quite long (~300 words) but front-loaded with the core flow and key guidance. Each sentence conveys useful information, covering invoke vs install, auth, payment, prompt library, and permissions. While it could be tightened, the structure is logical and no sentence is wasted.

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 tool with 23 parameters, 14 actions, no output schema, and limited annotations, the description is remarkably complete. It clarifies the intend-to-execution pipeline, runtime behaviors (links, retries), authorization requirements, and the separate prompt library subsystem. Agents can confidently use this tool without ambiguity.

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 0% schema description coverage, the description must compensate. It explains the central 'action' enum and the core flow (search→describe→invoke), clarifying which parameters matter for each action (mcp_id, tool_id, arguments, etc.). It doesn't detail every parameter like limit or prompt_vars, but given the tool's many actions, it provides enough semantics for correct usage. A 4 is appropriate; a 5 would require per-parameter details.

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 purpose: it is the official mcp.ai marketplace catalog and execution platform. It explicitly names the core actions (search, describe, invoke, install) and distinguishes itself from siblings like authenticate or show_version. It also covers the prompt library aspect, leaving no ambiguity about scope.

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?

Provides explicit guidance on when to use each action: prefer invoke for one-off runs (even without installation), use install only for permanent additions, list_tools for current callable tools, and subscribe/cancel for billing. It also explains when to use search_prompts/get_prompt for prompt text. This fully addresses selection between alternatives.

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