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

Goes beyond the readOnly/idempotent annotations with two genuinely new behavioral facts: it is FREE, and it never raises a protocol error on bad input, instead returning an error object with fix guidance, making retry-after-correction safe. It does restate the annotation hints ('read-only and idempotent'), which is redundant, and the wpm parameter's behavioral effect (values below 60 clamped to 60) is left entirely to 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?

Front-loaded with the verb phrase and the free/read-only facts, followed by example, usage rule, and error contract in a logical order. The inline JSON input/output sample is slightly bulky relative to the information it conveys, given an output schema already exists.

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?

Covers purpose, alternative routing, error behavior, and retry safety — the pieces an agent actually needs — and an output schema exists so return values need little explanation. Completeness is only slightly undercut by not noting the wpm override, the one non-obvious input beyond the required 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?

Schema coverage is 100%, so both parameters are already documented, and the baseline would be 3. The description adds value with a concrete typical-input example ('{"text": "<your article>"}') that shows the minimal viable call shape, though it never mentions the wpm knob, so it does not fully cover parameter space.

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 and resource ('Estimate reading and speaking time plus basic content stats') and immediately differentiates from the sibling analyze_writing by naming what it does not cover (writing quality, grade level). An agent can select it without opening 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?

'Use when length and pacing are the question. Not for writing quality or grade level (analyze_writing)' gives an explicit when, an explicit when-not, and names the alternative tool. This is exactly the routing information an agent needs among the seven siblings.

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