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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower; the description still adds genuinely useful traits beyond them: credit cost (12 per successful call), free sandbox behavior, and determinism. It does not describe output shape, but an output schema exists.

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?

Purpose is front-loaded, followed by tightly scoped notes on cost, determinism, and a single compact example. The long example JSON is the only mild overhead but it earns its place as usage illustration.

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 an output schema present, return values need not be explained, and the description covers cost, determinism, sandbox behavior, and the partner object shape. The unaddressed referenceDateIso is the main remaining gap for an otherwise complete definition.

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% with rich per-field descriptions, so the baseline is 3. The description adds the fact that `name`/`gender` are optional plus a worked example, but does not explain referenceDateIso or the semantic effect of omitting `time`.

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 resource (compatibility of two charts) and clarifies the mechanism ('computes both charts and reads them together'), which separates it from the single-chart get_chart sibling. It does not explicitly name the sibling it differs from, keeping it just short of a 5.

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 context of comparing two partners is implied, and the example shows the expected two-partner shape, but there is no explicit when-to-use guidance, no when-not conditions, and no routing to alternatives like get_chart or interpret_domain.

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