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

With no annotations, the description carries the full burden and does disclose the most consequential trait: paid $0.005 USDC per call via x402 through _meta["x402/payment"], plus a free 3-row sample escape hatch. It does not cover response shape, error behavior, or rate limits, which keeps it short of 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?

Three dense sentences: identity, routes/params, then payment and sample. Front-loaded with the resource and nothing repeated. The list of consumer use cases (localisation tools, language-learning apps, games, AI pipelines) is mild filler but occupies only one 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?

Given a nested params object and no output schema or annotations, the description covers routing, filter names, placeholder substitution, cost, and the free preview — enough to invoke correctly. The remaining gap is what a returned language record contains, which the description only gestures at with 'language metadata'.

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%, so the baseline is 3, but the description adds real meaning: it enumerates the /search query parameters (q, country, family, endangerment, limit, offset) that the schema only alludes to via a generic params object, and clarifies that {code} is a placeholder to substitute (e.g. /HND).

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 the resource (World Languages, Glottolog) and the concrete data it returns (language metadata for localisation, learning apps, games, AI pipelines), plus the two routes it exposes. An agent can distinguish it from siblings like regions or airports by domain, though the description never frames the operation as a verb (search/lookup).

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?

Names the two routes and the filter parameters that belong to /search, which implies when to use which route, and calls out sample=true as the free-preview path. There is no explicit routing advice (e.g. use /search when you have a partial name, /{code} when you have an ISO/Glottolog code) and no comparison to sibling data APIs.

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