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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so safety and side-effect behavior are covered. The description adds the equivalent REST endpoint, which aids mental mapping, but says nothing about return format or the 10,000-character truncation behavior (which lives only in the schema).

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 short sentences, front-loaded with the operation and followed by the endpoint reference. Nothing is padded, though the endpoint mapping is arguably optional.

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 should ideally clarify what the counts look like in the response, and it only implies this through the verb 'count'. Combined with the missing differentiation from textStats, an agent has enough to call the tool but not full confidence about output shape or sibling selection.

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 100%, so the schema already documents case, char, and the 10,000-character limit on text. The description's phrase 'a letter or substring' loosely maps to the char parameter but adds no syntax or default details beyond the schema. 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?

The description names a specific verb (count) and enumerates the exact resources measured: characters, words, bytes, and occurrences of a letter or substring. That is clear and concrete. It does not, however, distinguish itself from the sibling textStats, which appears to overlap in purpose.

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 guidance on when to use this tool versus alternatives such as textStats, nor any stated preconditions or exclusions. The only auxiliary information is an equivalence to an HTTP GET endpoint, which is context rather than usage direction.

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