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

Annotations already cover read-only and open-world safety. The description adds genuinely new context beyond them: the 20-item batch ceiling and that responses contain per-component ingredient and allergen breakdowns, which tells the agent the depth of the data returned.

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?

Two sentences, zero waste. The core capability and scope are front-loaded, followed immediately by the sibling routing instruction.

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 read-only annotations, a fully described 2-param schema, and an output schema present, the definition covers what an agent needs. The only minor gap is not describing the country/item_ids coupling ('must match the market') in the description, though the schema carries 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 description coverage is 100%, so both parameters (country's allowed markets and default, item_ids format and limit) are already fully documented in the schema. The description's 'up to 20 items' reiterates the schema limit rather than adding new meaning, so baseline 3 applies.

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+resource ('Fetch nutrition and allergen details') with a precise scope ('up to 20 McDonald's items') and detail level ('ingredient and allergen breakdowns by component'). It explicitly distinguishes itself from the mcdonalds_item sibling.

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?

Directly routes the agent to the alternative: 'Use mcdonalds_item for one item's simpler detail.' That is a clear conditional for choosing between the two, though it doesn't state when-not to use this tool in general terms (e.g., for menu browsing).

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