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

Annotations already cover read-only, non-destructive, closed-world behavior, so the description's added value is the counting semantics: words are letter/digit runs, hyphenated words and contractions count once, paragraphs split on blank lines, and reading time uses a stated 238 wpm rate. The 100 KB input cap is a genuinely useful operational limit. It stops short of stating the response shape.

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, front-loaded with the outputs produced, then edge-case rules, then the size limit. Every clause carries information an agent could act on; nothing is padding.

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?

With no output schema, the description does the work by enumerating the metrics computed and the reading-time constant. The remaining gap is the concrete return structure (field names, whether characters-with-spaces and characters-without are separate keys), which is not spelled out.

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 a single parameter with 100% schema description coverage ('The text to analyze'), so the schema already carries the parameter burden and the baseline applies. The description adds normalization rules for how that text is interpreted, but nothing about the parameter itself (encoding, whitespace handling, truncation at 100 KB).

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 a specific verb ('Count') plus the exact set of resources: words, characters with/without spaces, sentences, paragraphs, and reading time. No sibling (base64, hash_text, format_json, etc.) overlaps, so the agent can route here unambiguously.

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?

Usage is only implied by the purpose statement; there is no explicit 'use this when...' framing or mention of alternatives. In practice the tool has no competing sibling, so the omission is low-risk, but the description does not actively guide selection.

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