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

Beyond annotations (readOnlyHint=false, openWorldHint=true), the description discloses that invoke runs uninstalled MCPs one-off, returns connect/checkout links when auth or payment is needed, and that writes require workspace owner/admin. It also reveals installed_in_toolkit vs installed_in_workspace status flags, adding significant behavioral context.

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 lengthy but each section adds distinct operational detail: core flow, invoke semantics, install vs invoke, permissions, and prompt library. It leads with a clear definition and is dense rather than redundant, though it could benefit from bullet points for readability.

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 23-parameter, 14-action tool with no output schema, the description is remarkably complete. It covers edge cases like auth/checkout links, permissions, billing, installed status, and the prompt library, leaving little ambiguity about the tool's overall behavior and scope.

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 adds meaning to the central 'action' enum by explaining each action's purpose (search, describe, invoke, install, etc.) and references key parameters like tool_id, mcp_id, and prompt_vars. However, many optional parameters (limit, query, immediate, tier_slug) are not explicitly described, though their names and defaults make them reasonably understandable.

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 identifies the tool as the mcp.ai marketplace, a catalog and execution platform for MCPs. It enumerates distinct capabilities (search, describe, invoke, install, subscribe, prompt library) and differentiates from sibling tools like authenticate and show_version.

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?

Provides explicit guidance: 'Use install only to make an MCP PERMANENT... prefer invoke for a single/occasional use' and outlines the core flow search→describe→invoke. It also contrasts list_tools and explains when to use subscribe/cancel/report_bug/request_mcp and the prompt library.

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