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

Beyond the annotations (readOnlyHint=false), the description adds rich behavioral context: invoke works even if the MCP is not installed, returns connect/checkout links for auth/payment, and runs one-off without bloating the toolkit. It also discloses that writes require owner/admin, and explains the prompt library behavior including shareable links. 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?

Despite being lengthy, the description is well-structured and front-loaded: it starts with the core purpose, then explains the core flow, then key details (invoke vs install), then auth/write permissions, and finally the prompt library. Every sentence adds value, and the density is appropriate for a tool with 23 parameters and 14 actions.

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?

The description is remarkably complete for the tool's complexity. It covers all major actions, their outcomes (e.g., describe returns full profile with pricing/auth), exception handling (connect/checkout links), permission requirements, and the prompt library's separate functionality. Without an output schema, it adequately describes return behaviors. Only minor edge cases (e.g., exact behavior of resume or subscribe) are not detailed, but overall it is exhaustive.

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%, so the description must compensate. It does explain the action enum in depth, mapping each action to its purpose and associated parameters (e.g., invoke uses tool_id and arguments, publish_prompt uses prompt fields). However, some parameters like immediate, tier_slug, conversation, and cancel_reason are not explicitly described, relying on schema defaults. Still, the description provides enough context for most parameters to be effectively utilized.

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 catalog and runner, with explicit verbs like search, describe, invoke, install, and a clear core flow. It distinguishes itself from sibling tools like authenticate or show_version by focusing on discovery and execution of MCPs and prompts.

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 explicit guidance on when to use invoke vs install: prefer invoke for single/occasional use, install for permanent integration. It also explains when to use search, describe, list_tools, subscribe, and request_mcp, clearly delineating scenarios like capability requests and billing needs.

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