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

Beyond the annotations, the description discloses important behavioral traits: invoke runs one-off without bloating the toolkit; describe returns full profile including pricing and auth; writes require workspace owner/admin; empty wallets trigger a checkout/top-up link; and the prompt library stores ready-made prompt text rather than MCPs. These details greatly exceed what the annotations alone communicate. No contradiction with the annotations' read/write hints exists.

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?

Despite being a dense paragraph, every sentence earns its place. The description front-loads the core flow and then structures the content: search → describe → invoke → install → billing/feedback/requests → prompt library. Each sentence delivers a distinct behavioral or usage fact, with no repetition or filler.

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 orchestrating dozens of actions with no output schema and weak annotations, the description is nearly all-comprehensive. It covers discovery, one-off execution, permanent installation, listing tools, billing, bug reporting, new-world MCP requests, and the prompt-library sub-feature, including return links for auth and payment. Missing details around individual parameters are the only real gap, and that's more of a schema-description problem than a tool-level completeness problem.

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 description coverage, the description must compensate, but it only covers the domain-level meaning of a few actions like action=search, describe, invoke, and prompt-related functions. It does not explain how concrete parameters such as limit, immediate, tier_slug, cancel_reason, prompt_body, prompt_vars, request_details, or conversation should be used. The high-level flow is clear, but mapping it to this large parameter surface is left to inference.

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's opening sentence clearly defines the tool: 'the official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them.' It covers specific actions such as search, describe, invoke, install, and the prompt library, making its purpose and scope unmistakable. It also distinguishes itself from sibling tools like report_bug or connect by enumerating its own capabilities.

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 offers explicit guidance: 'use install only to make an MCP PERMANENT... prefer invoke for a single/occasional use,' and states that 'invoke works even when the MCP is NOT installed.' It also provides conditional behavior for credentials, payments, ownership, and alternatives like list_tools, subscribe/cancel, report_bug, and request_mcp. This is exceptionally complete when-to-use-and-when-not-to-use guidance.

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