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

Annotations already declare read-only, idempotent, non-destructive, and closed-world behavior, but the description adds important context beyond them: it is free, it shows the error-object contract instead of raising protocol errors, and it gives a concrete invalid-input example. It also confirms retry safety after correcting input. This is richer than the annotations alone.

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?

The description front-loads the purpose and usage guidance, and the example output and error contract are useful. It is slightly longer than strictly necessary because it includes both return-value and error examples, but the structure is clear and most content earns its place.

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?

The tool has an output schema, annotations covering safety, and a fully documented single parameter, so the description does not need to carry those burdens alone. It still adds the critical usage distinction from ai_tell_scan and the non-protocol-error behavior, making the definition complete for correct selection and invocation.

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 only one parameter, and schema coverage is 100%, with the schema already stating that 'text' needs at least 3 sentences. The description shows a typical input shape and an error example, but adds little semantic detail beyond the schema's existing documentation of the parameter. The baseline of 3 is appropriate.

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 states a specific verb and resource: 'Map a draft's sentence rhythm and find where it goes flat.' It also names the concrete outputs, sentence lengths and burstiness coefficient, and explicitly distinguishes itself from the sibling ai_tell_scan. An agent can identify the tool's role without inspecting the schema.

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?

It explicitly says when to use it: 'Use when prose reads flat and sentence-length pattern is the suspect.' It also says when not to use it and names the alternative: 'Not for a full inventory of tells (ai_tell_scan).' This is explicit routing guidance.

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