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

The description goes far beyond annotations, disclosing that invoke works without installation, that it handles credential/payment flows via links, that install makes MCPs permanent, and that search/describe flag installed status. It also introduces the prompt library as a separate capability. No contradictions with annotations (readOnlyHint=false is consistent with write actions described).

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 a single dense paragraph with no formatting or bullet points. While it packs a wealth of information, it is not front-loaded with the most critical info first and requires careful parsing. For a tool with this many capabilities, some structure would improve readability. It is overly long but every sentence carries value.

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 complexity (23 parameters, 14 actions, no output schema), the description covers the core flows, edge cases (credentials, payment), permission requirements, and even the separate prompt library. It explains the distinction between installed and not-installed MCPs and when to use each action. This is remarkably complete for such a multifaceted tool.

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 0%, but the description compensates by explaining the purpose of key parameters like action, query, mcp_id, tool_id, arguments, and prompt-related fields within the flows. However, it does not explicitly document all 23 parameters (e.g., limit, immediate, tier_slug, cancel_reason), leaving some ambiguity for less central parameters. Still, it adds substantial meaning beyond raw names and defaults.

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 is the official mcp.ai marketplace that catalogs and runs MCPs/tools, and explicitly lists the core flow (search → describe → invoke). It distinguishes itself from siblings by being the central marketplace entity, and differentiates actions like invoke vs install.

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 for when to use invoke (one-off) vs install (permanent), when to use list_tools, subscribe/cancel for billing, report_bug, request_mcp for new MCPs, and the prompt library functions. Also notes that writes require owner/admin and that invoke returns connect/checkout links for credential/payment obstacles.

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