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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is fully covered. The description does add a genuine behavioral trait beyond the name — the SEO/social limit comparison — but omits the 200,000-character input cap and says nothing about how results are reported.

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?

A single tight sentence with zero padding, front-loading the enumeration of counted units before the comparison feature. Only minor awkwardness in the trailing clause keeps it from being exemplary.

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 return values need no explanation, and annotations carry the safety profile. The description covers the tool's capability set adequately; only the input size limit and the count methodology remain unstated.

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?

One parameter with 100% schema description coverage, so the schema already documents 'text'. The description adds no syntax, formatting, or edge-case guidance (e.g., how graphemes vs code points are counted) beyond what the schema provides. Baseline 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?

States a specific verb (count) and enumerates the exact units measured: words, code points, graphemes, sentences, paragraphs, plus an SEO/social limit comparison. This implicitly separates it from the nearest sibling count_tokens, though it never names that alternative explicitly.

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: the mention of SEO and social limits suggests the use case of validating copy against platform limits, but there is no explicit when-to-use statement, no exclusions, and no pointer to count_tokens for token-based counting.

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