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

With readOnlyHint/destructiveHint already declaring safety, the description still adds substantial non-structured context: the 20,000-character ceiling, local processing, per-call pricing ($0.01 via x402 USDC or card key /credits), the first-25-free allowance, and that failed calls are free. It even explains the non-idempotent hint ('each call is charged, so repeats are not free') and confirms mutability boundaries ('Reads or computes only and changes nothing'). No contradiction with annotations.

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?

Front-loaded with the core 'one call' framing and the output inventory, with cost/limits after. The first sentence is a very long run-on list, and some clauses (e.g. x402 vs card key detail) are dense, but every sentence carries usable information rather than filler.

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?

No output schema exists, yet the description compensates by enumerating the returned sections (length, reading time, readability grade, keywords, repeated phrases with density, entities, injection scan). Combined with size limit, cost model and safety semantics, an agent has everything needed to decide to call it and to interpret the result.

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?

There is only one parameter and the schema already documents it fully ('The text (up to 20,000 characters)'), so the description's 'Up to 20,000 characters' merely restates the constraint. Nothing is added about encoding, truncation behavior, or what happens if the limit is exceeded, so the high-coverage baseline of 3 applies.

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?

Names a specific verb and resource ('One call to analyse a text') and then enumerates the exact sub-analyses returned: length, reading time, readability grade, keywords, phrase density, PII-like entities and a prompt-injection scan. That enumeration also implicitly distinguishes it from the granular siblings (text_stats, ai_keywords, text_prompt_injection, text_keyword_density), which an agent can infer without opening any schema.

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?

Gives three concrete usage contexts ('review drafts, triage inbound messages or vet scraped content') and signals a bundle-vs-singles tradeoff ('Cheaper than the four tools bought one by one'). It stops short of explicitly naming the alternative single-purpose tools or saying when a narrower sibling is preferable (e.g. if you only need a prompt-injection check).

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