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

Annotations already declare readOnlyHint=true and openWorldHint=true, and the description does not contradict them. Beyond annotations, it discloses cost ($0.10 per call), the counting rule for lightly reworded sentences (one removal plus one addition), the underlying sentence-level diff basis, and the former name. It does not describe rate limits or exact output format, but those are minor given the annotations.

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 is three sentences and front-loads the definition, then clarifies scope, then gives the sibling alternative, former name, and cost. Each sentence carries distinct and useful information, though the inclusion of both a former name and cost might be considered optional. Overall, it is well-structured and efficient.

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 must explain the return value and any implicit behavior. It states the result is a percent with a 'magnitude band' but never defines the band values or how they map to output. It also does not specify which years are compared (only 'year over year' without clarifying the base year selection). These gaps make it incomplete for an agent that needs to interpret results.

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 baseline is 3. The description does not add explicit parameter-level meaning beyond what the schema states; however, it introduces the 'year over year' concept that implies the tool compares the latest filing to the prior year—a behavior not captured in the schema and not clarified further. This omission keeps it at the baseline.

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 defines the metric precisely: 'added sentences divided by total sentences in the newer section, as a percent, with a magnitude band'. It explicitly states what it measures (editing activity) and what it does not (risk/exposure), and names the sibling compare_filings as the alternative for raw passages. This leaves no ambiguity about the tool's function.

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?

The description provides both positive and negative usage guidance: it says this measures editing activity, not risk or exposure, and explicitly directs users to compare_filings when passages are needed ('buy that when you need the passages themselves'). It also notes the former name still answers, aiding legacy users. This clearly routes an agent to the correct tool.

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