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

Goes well beyond the annotations: discloses pay-per-call pricing ($0.005 via x402, USDC on Base, MCP payments Base-only), that failed/no-match/source-down calls are not charged, data licensing and attribution per source, that allergens may be incomplete, and that returned content is untrusted third-party data. This is exactly the behavioral context annotations cannot carry.

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, but the body is a dense run-on that crams pricing, terms URL, licensing, and error-charging policy into one paragraph, including a malformed clause ('Bad input, no match or source down: not charged on Base'). Valuable content, but not well-structured.

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?

No output schema, so the description must convey returns; it lists the per-100g nutrient fields and sources plus attribution caveats. It stops short of describing the per-item response shape or how multiple matches per item are structured, which an agent would need for parsing.

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 baseline is 3; the description adds real value by tying q to grocery_normalize canonicalIds, clarifying barcode is a GTIN read live from Open Food Facts, noting n is 1-5 USDA matches, and stating 'one price per call' for the 10-item cap.

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 ('Ingredient nutrition facts API') and enumerates both access shapes (GET with q/barcode, POST batch of up to 10). It links q to the grocery_normalize canonicalId, partially differentiating from that sibling, though the dense API-doc phrasing makes the core purpose slightly harder to extract than a plain sentence would.

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?

Implied usage comes through the parameter walkthrough: single lookup via GET, batch up to 10 via POST, barcode reads live from Open Food Facts. But there is no explicit 'use this instead of X when...' guidance and no stated alternatives besides the canonicalId pointer to grocery_normalize.

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