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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantive behavior beyond them: a 6-item cap, products counted at the most each label suggests per day, fish-oil amounts counting EPA+DHA, and how hidden amounts are flagged. This is rich context an agent could not infer from structured fields.

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 purpose followed by examples and return shape; every sentence carries information. It runs long, but no sentence is filler given the absence of an output schema.

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 proactively describes the return shape (totals with sources and UL comparison, other_totals, items, not_found), and the input constraints are fully covered. An agent has everything needed to call and interpret it.

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 the baseline is 3, but the description adds value over the schema: the 'up to 6 items' limit, semicolon separation, and the country=GB NHS-guidance behavior beyond the schema's terse example.

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: 'Add up everything someone takes and check the daily totals against adult upper limits.' The multi-item 'stack' scope implicitly separates it from check_dose (single dose) and get_nutrient, though no sibling is named explicitly.

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?

Gives explicit when-to-use examples ('I take Centrum, vitamin D 5000 IU and zinc 50 mg, is that too much?'), which anchors the trigger condition well. It does not name an alternative or state when NOT to use it (e.g., for a single item, use check_dose).

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