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

Beyond the annotations (readOnlyHint=false, openWorldHint=true, etc.), the description discloses key behavioral traits: invoke works even when the MCP is not installed, runs one-off without bloating the tool list; credentials and payment edge cases (returns connect link or checkout/top-up link); permission requirements ('Writes ... require workspace owner/admin'); and installed_in_toolkit vs installed_in_workspace flags. These add substantial context not available from annotations alone.

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 dense with valuable information, organized around the core flow and key distinctions. Each sentence adds meaningful content, and the use of 'KEY:', 'Core flow:', and conditional statements provides structure. A slight deduction because it could be split into sections or trimmed for easier scanning, but no sentence is wasted.

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 with 23 parameters, 14 actions, no output schema, and moderate annotations, the description covers a remarkable amount: the main flow, edge cases for credentials/payments, permission levels, and the prompt library. However, it does not describe the exact response format for key actions like search/describe/invoke, and leaves several parameters (immediate, tier_slug, cancel_reason) undone. The description is robust but not fully complete given the tool's complexity.

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 explains the meaning of the central 'action' parameter by enumerating values and their flow, and clarifies key parameters like tool_id, mcp_id, and the prompt_* family. However, several parameters (limit, immediate, tier_slug, cancel_reason, conversation, prompt_targets, etc.) receive little or no explanation, leaving the agent to infer meanings from the schema enums 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 states a specific, multi-faceted purpose: 'the official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them.' It clearly distinguishes the tool from siblings by highlighting its role as a catalog and execution platform, and it enumerates distinct actions (search, describe, invoke, install, list_tools, etc.) with a clear core flow.

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 each action and preference ordering: 'Core flow: action=search discovers MCPs by intent → describe returns one MCP's full profile ... → invoke RUNS that tool.' It explicitly contrasts invoke vs install: 'prefer invoke for a single/occasional use... Use install only to make an MCP PERMANENT in the active toolkit.' Also clarifies when to use list_tools, search_prompts, get_prompt, and publish_prompt.

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