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

Annotations already establish readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description goes beyond that with genuinely non-obvious behavior: the tool charges $0.002 USDC per call via x402, and it returns derived analytical output (readability scores, keyword density) rather than a simple transform. Only the return shape and any input-size limits remain undisclosed.

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?

One front-loaded sentence starting with 'Text statistics:' plus a short billing sentence. The metric list is dense but each item is informative for a tool that computes many outputs; nothing is padded or repeated.

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?

Since there is no output schema, the enumerated metric list usefully compensates by telling the agent what comes back, and the cost is disclosed. However, no input constraints, size limits, or failure modes are given, leaving an agent unable to predict behavior on long or non-English text.

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?

With one required parameter and 0% schema description coverage, the description carries the input burden. It never describes the 'text' parameter — no length limits, language assumptions, or formatting constraints — though a single self-evidently named string parameter keeps the gap small.

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 the exact resource (text) and enumerates the specific metrics produced — word/character/sentence counts, readability scores (Flesch, Flesch-Kincaid, Gunning fog), reading/speaking time, keyword density, longest sentences. An agent can tell it computes analytics rather than transforming text, but no sibling is named to disambiguate it from tokens_count or summarize.

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?

There is no when-to-use guidance, no prerequisites, and no exclusions. Faced with siblings like tokens_count, text_rewrite, and summarize, the agent gets no signal about which to pick for a given intent.

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