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

The annotations already indicate non-read-only, non-idempotent, open-world behavior. The description adds meaningful context: writes require owner/admin, invoke returns connect/checkout links for auth/payment follow-up, install is permanent while invoke is one-off, and search/describe flag installation status. It does not describe all possible side effects (e.g., uninstall consequences, billing side effects), but it covers the major behavioral traits. No contradiction with annotations; this is solid disclosure.

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 (about 280 words) but dense and front-loaded with the core flow (search → describe → invoke). Each sentence adds essential information about capabilities, key behaviors, or usage distinctions. It could be more structured (e.g., bullet points) for easier parsing, but given the tool's complexity and multiple action families, the prose is justified and not redundant.

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?

With 23 parameters, no output schema, and complex multi-action behavior, the description covers the essential context: a clear core flow, the distinction between invoke and install, auth/payment handling, owner permissions, prompt library, and even workspace/toolkit flag semantics. It lacks explicit return structures for each action (e.g., what search returns beyond results), but given the absence of an output schema and the extensive prose, it is reasonably complete for an agent to use the main flows.

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 `action` enum and high-level concepts (e.g., tool_id, arguments, prompt slugs) through the core flow, but the majority of the 23 parameters—`limit`, `immediate`, `conversation`, `prompt_targets`, `cancel_reason`, `report_context`, etc.—are never defined. An agent would have to guess at required values for many auxiliary actions, making correct invocation difficult. The description only partially compensates for the missing schema descriptions.

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 explicitly identifies the tool as 'The official mcp.ai marketplace — the in-platform catalog of every MCP/tool, AND the way to run them.' It clearly states its function (discover, describe, invoke, install, manage MCPs and prompts) and distinguishes it from sibling tools by being the central hub. The verb+resource is specific: it's the marketplace that both catalogs and runs MCPs/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 thorough guidance on when to use each action: use invoke for one-off runs, install for permanent installation, list_tools to see what's callable, subscribe/cancel for billing, request_mcp for new tools, and the search/describe flow for discovery. It also explains key nuances like 'invoke works even when the MCP is NOT installed' and that writes require workspace owner/admin. This explicitly frames when to use this tool and its internal actions, going beyond mere existence.

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