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

Beyond the annotations, the description reveals key behaviors: invoke works even when the MCP is not installed and runs a one-off tool without adding it to the toolkit; missing credentials return a connect link; empty wallet returns a top-up link and instructs to retry; writes require workspace owner/admin. These are important behaviors not encoded in annotations, making the agent prepared for edge cases.

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?

Although long, the description is dense and structured: it flows from catalog definition to core flow to key behavior to install-vs-invoke to permissions to the prompt library. Every sentence adds new information; there is no fluff or repetition. It is organized as a single coherent guide.

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 complexity (23 parameters, no output schema, no schema description coverage), the description covers all major operational scenarios: discovery, detail retrieval, invocation, installation, uninstallation, billing, permissions, and prompt library usage. It even explains edge cases (missing credentials, empty wallet) and retry logic. This is a complete operational manual for the agent.

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 description coverage is 0%, but the description compensates by explaining the meaning of the main action parameter and the workflow: 'action=search discovers MCPs by intent → describe returns one MCP's full profile... so you pick the right tool_id → invoke RUNS that tool.' It also covers the prompt-related actions. However, many parameters (limit, immediate, tier_slug, cancel_reason, etc.) remain unexplained, leaving gaps for less central parameters.

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 opens with a clear statement: 'The official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them.' It then explains the core flow (search → describe → invoke) and distinguishes the marketplace's role from sibling tools like authenticate or toolkit_info. It is specific about the resource and the verbs involved.

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 explicitly contrasts invoke vs install: 'Use install only to make an MCP PERMANENT in the active toolkit... prefer invoke for a single/occasional use.' It also states when to use search/describe, when to use request_mcp, and clarifies that report_bug sends feedback. This gives clear 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.