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

Beyond the annotations (readOnlyHint=false, openWorldHint=true, etc.), the description discloses critical behaviors: invoke works even if the MCP is not installed, returns connect/checkout links when needed, and does not bloat the toolkit. It also explains the prompt library separately, and notes that writes require privileged roles. 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 long but front-loaded with the core purpose and flow, then dives into key distinctions (invoke vs install, permissions) and auxiliary features (prompt library). It uses formatting like 'KEY:' and 'USE' to guide attention. Every sentence adds value, though the single-paragraph format with many clauses makes it dense; a few more line breaks would improve scannability without losing content.

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 high complexity (14 actions, 23 params, permissions, auth/payment flows, prompt library), the description covers the major usage patterns, prerequisites, and side effects. It explains the search/describe/invoke chain, install vs invoke semantics, credential/top-up handling, and the prompt library. It does not detail exact return formats for every action (e.g., list_tools output), but that is beyond the essential context.

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 schema description coverage at 0%, the description compensates by explaining the key workflow parameters: action values (search, describe, invoke, etc.), mcp_id, tool_id, arguments, and prompt-related params like prompt_vars and prompt_slug. It connects parameters to concrete steps (e.g., 'describe returns... so you pick the right tool_id → invoke RUNS that tool'). However, not all 23 parameters are individually explained; some defaults and optional ones are left implicit.

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 it is 'The official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them.' It enumerates a core flow (search → describe → invoke) and lists 14 distinct actions, making it unmistakable what the tool does. It distinguishes itself from siblings by being the central catalog/execution hub, covering capability requests like 'find an MCP that does X'.

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?

Explicit guidance is provided: 'USE install only to make an MCP PERMANENT in the active toolkit... prefer invoke for a single/occasional use.' It also states permission requirements ('Writes require workspace owner/admin') and clarifies when to use search vs describe vs invoke. Alternatives are implied through the flow description.

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