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

With no annotations, the description carries the full burden and does well: it discloses billing (€0.001 per request), the auth mechanism (Bearer key in Authorization), an input size cap, and graceful degradation for unsupported languages. It stops short of describing failure modes, rate limits, or whether the call is cached/idempotent.

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 core capability and language coverage are front-loaded, and the trailing sentence packages limits, cost, auth, and parameters efficiently. The semicolon-heavy packing is dense but every clause carries new information.

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?

An output schema exists, so the description needn't explain return values, and it covers the remaining gaps an agent needs: language coverage, input size limit, cost, auth, and fallback behavior. Only edge-case handling (errors, oversized input) is unaddressed.

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, and it does: it defines text as the content to score, language as an ISO-2 code with an effective default of en (the schema only shows null), and explains what happens when the language is unsupported. That is meaningful semantics beyond the bare schema, though format examples for the language codes are absent.

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 names a specific verb (score) and resource (readability), and enumerates the exact metrics returned (Flesch, FK grade, Gunning Fog, SMOG, Coleman-Liau, ARI) plus the supported languages. Purpose is unambiguous. It does not explicitly contrast with near-neighbors like detect_lang or summarize, so it stops short of a 5.

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?

It supplies useful operating context — 100 000 char ceiling, per-request cost, and the conditional rule that unsupported languages receive only language-independent metrics — which effectively tells the agent when the tool is and isn't a good fit. However, there is no explicit statement of alternatives (e.g., use detect_lang first, or summarize instead) or of when not to call it at all.

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