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

With no annotations, the description carries the full burden and does well: it explains natural-language identification, quantity/unit resolution, one result per query, and per-item error returns. It leaves out ambiguity handling, rate limits, or permission context, so it is strong but not fully exhaustive.

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 front-loaded with purpose and usage, then structured around behavior and returns. It is clear and mostly efficient, though the detailed return-field enumeration is somewhat redundant because an output schema 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?

For a one-parameter lookup tool with full schema coverage and an output schema, the definition includes the key context: what it returns per query, error behavior, and the photo alternative. Nothing essential for correct invocation appears to be missing.

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%, and the schema already documents plain names, quantity+unit formats, barcodes, defaults, and splitting compound foods. The description adds only a light restatement that each query describes one food item and that the API resolves quantity/unit, so baseline 3 is appropriate.

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 states a specific verb and resource: "Look up nutrition facts for one or more foods described in plain text." It also explicitly distinguishes this text-based lookup from analyze_food_image for photographs, so the agent can select between siblings without opening schemas.

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?

It gives clear trigger conditions: use for questions about calories, macros, or nutrients for a named food or meal. It also names the photo alternative and when to use it, covering both when to use this tool and when to switch to the sibling.

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