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

Annotations already declare read-only, idempotent, non-destructive behavior, and the description adds genuinely new traits: no credit metering and the guarantee that unknown discovery dates are omitted rather than guessed. It does not cover pagination or response shape, which keeps it below a 5.

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?

Four short sentences, front-loaded with the ranking criterion and followed by cost and data-quality caveats. The trailing limit restatement duplicates the schema and is the only wasted clause.

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 single optional parameter with no output schema, the description supplies the ordering, the cost model, and the null-handling rule that an agent needs. The return fields are only referenced indirectly via 'same payload as GET /v1/recent', requiring external knowledge.

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 coverage is 100% and the single limit parameter is fully documented there; the description only restates the 1–50 range and default 20. Baseline 3 applies since the schema carries the parameter semantics.

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?

States a specific resource and ordering criterion: newest MCP servers ranked by real first_seen_at, with a concrete payload reference (GET /v1/recent). It is clearly not a filtered search like census_search, though it never names a sibling to contrast with explicitly.

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?

'Unmetered' and 'Only rows with a known first-seen date' give useful scope context for choosing this endpoint, but there is no explicit when-to-use versus census_search or census_changes, and no stated exclusions.

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