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

Annotations only declare readOnlyHint=true and openWorldHint=true; the description goes beyond them with two meaningful disclosures: a per-call price of $0.007 USDC via x402 (payment/auth context) and a hard cap of 3 variants. It also states the 'every fact kept' constraint, which is a real behavioral guarantee. It stops short of 5 because nothing is said about rate limits, failure modes, or how variants are returned.

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?

Two sentences, front-loaded with the core verb and resource, with no filler. The 12-value tone list makes the first sentence long and list-heavy, which slightly hurts scanability, but every clause carries 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?

For a 5-parameter tool with no output schema, the definition is mostly sufficient: input semantics are covered and the cost is disclosed. What is missing is any indication of the return shape (single string vs. an array of up to 3 variants) and any note on whether tone/length are free-form strings or must match the listed values — the latter matters given the schema declares no enum.

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% and the schema declares no enums, so the description carries the full burden — and it largely does. It enumerates all 12 valid tone values (a substitute for a missing enum), and gives meaning to length ('shorter or longer'), audience ('for an audience'), and variants ('up to 3 variants'). Only 'text' is left implicit, which is self-evident.

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 opens with a specific verb+resource ('Rewrite text') and immediately scopes what rewriting means here: tone, audience, length, grammar fixes, fact preservation, and a variant cap. That is far more specific than the bare name. It does not, however, distinguish itself from plausible siblings like translate, summarize, or prompt_optimize, which is why 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?

The description says what the tool can do but never says when to reach for it over alternatives. With siblings such as translate, summarize, text_diff, and prompt_optimize in the catalog, the absence of any routing guidance or exclusions leaves the agent to infer the use case.

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