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

The description goes well beyond annotations by disclosing critical behaviors: invoke works even when the MCP is not installed, returns a connect link if credentials are needed, and returns a checkout/top-up link if payment is required. It also states that writes (install/uninstall/subscribe/cancel and the one-off install behind invoke) require workspace owner/admin, and that search/describe flag installed_in_toolkit vs installed_in_workspace. These details provide rich operational context not available in the 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 well-structured, starting with the high-level purpose and then explaining the core flow, key behaviors, permissions, and the prompt library. Every sentence delivers meaningful information, and the logical flow from search → describe → invoke → install makes it easier to follow. It is not as brief as ideal, but the complexity of 14 actions and 23 parameters justifies the length.

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 14 actions, 23 parameters, and no output schema, the description provides a strong overview of the marketplace, covering search, describe, invoke, install, uninstall, list_tools, subscribe/cancel, report_bug, request_mcp, and the prompt library. It explains important edge cases like connect links and checkout links. However, a few actions (e.g., resume) and parameters (e.g., conversation) are not addressed, leaving some gaps in an otherwise comprehensive description.

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?

The description adds meaning to core parameters like action, mcp_id, tool_id, and arguments through the explained flow (e.g., 'describe returns one MCP's full profile ... so you pick the right tool_id → invoke RUNS that tool'). However, with 23 parameters and 0% schema coverage, many parameters such as query, limit, prompt_* fields, cancel_reason, and request_details are not explained. The description provides a high-level flow but does not systematically cover each parameter's purpose, so it only partially compensates for the coverage gap.

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 'The official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them,' clearly stating the tool's purpose and scope. It distinguishes itself from siblings by covering the entire catalog and execution layer, not just a single function. The description also enumerates the main actions, showing it is the central marketplace and execution hub.

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 which action: 'Core flow: 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 contrasts invoke vs install: 'prefer invoke for a single/occasional use' and 'Use install only to make an MCP PERMANENT in the active toolkit.' It additionally clarifies list_tools for current callable tools, subscribe/cancel for billing, and request_mcp for new MCPs, giving clear decision-making instructions.

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