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

With no annotations, the description carries the full burden. It discloses key behavioral traits: a 'query-free discovery receipt' is included in the result set, and eligible provider-funded actions appear separately without changing organic order. This goes beyond a simple listing and informs the agent about sponsored content handling and an unexpected receipt element.

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 exactly two sentences, with the primary purpose front-loaded in the first sentence and behavioral context in the second. There is no filler or redundancy, and every clause serves a purpose.

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 effectively covers purpose, ranking, behavioral quirks, and the recommended pairing with verify_mcp. Although there is no output schema and the return format is not described, the tool is straightforward and the schema covers input parameters well, making the description adequate for selection and invocation.

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 input schema provides complete descriptions for all three parameters (limit, query, category) including enum values. The description adds no parameter-specific meaning beyond this, so with 100% schema coverage, the baseline of 3 is appropriate.

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 first sentence explicitly states 'List sites in the index that expose a live MCP server, ranked by agentic readiness.' This provides a specific verb and resource, and the ranking criterion differentiates it from siblings like get_top_sites and search_agents. The pairing with verify_mcp further clarifies its unique role.

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 gives clear context by stating the tool is for discovery of live MCP servers and suggests pairing with verify_mcp for a probe-before-use workflow. However, it does not explicitly contrast with alternatives like search_agents or state when not to use it, so it lacks explicit exclusion criteria.

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