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

Beyond the annotations (which only provide hints like readOnlyHint=false and openWorldHint=true), the description reveals critical behavioral details: invoke works even if the MCP is not installed, does not add it to the toolkit, returns connect links for auth, returns checkout links for payment, and requires workspace owner/admin for writes. It also discloses that search/describe flag installed status and that install/uninstall/subscribe/cancel are persistent. 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?

The description is information-dense but delivered as a single unbroken paragraph, making it hard to scan. It leads with the main purpose and then covers core flows, caveats, permissions, and the prompt library, but could benefit from bullet points or short sections. It is not tautological, but its length and lack of structure reduce its efficiency.

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?

Given the tool's enormous scope (14 distinct actions, 23 parameters, no output schema, sparse annotations), the description covers the major workflows: search/describe → invoke, install/uninstall, billing, permission requirements, and the prompt library. It omits details on return values and some sub-action behaviors, but for an agent selecting and invoking the tool, the essential context is present.

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 23 parameters and 0% schema coverage, the description must compensate. It explains the central 'action' parameter and key related parameters (tool_id, arguments, prompt_* fields) by describing the actions they drive. However, many parameters (limit, immediate, tier_slug, conversation, request_details, cancel_reason, etc.) remain semantically opaque, leaving the agent without full parameter understanding despite the description's effort.

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 identifies the tool as 'the official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them,' with an explicit scope covering catalog search, MCP execution, and prompt library access. It uses explicit verbs and resources (search, describe, invoke, install, list_tools, search_prompts, etc.) and distinguishes itself from sibling tools by defining its unique marketplace role.

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 provides detailed when-to-use guidance: 'prefer invoke for a single/occasional use,' 'Use install only to make an MCP PERMANENT,' and clarifies when credentials or payment are needed ('invoke returns a connect link' / 'checkout/top-up link'). It also distinguishes search/describe from list_tools and separates prompt library functions from MCP operations, giving clear alternatives.

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