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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a useful conditional ('include calories when the source provides them') but says nothing about pagination, response size, or whether the full menu is always returned. Some added value, but not rich behavioral context.

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 tight sentences, front-loaded with the core action and resource, followed by the sibling-routing clause. Zero filler.

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 single-parameter read tool with an output schema and annotations covering the safety profile, nothing an agent needs to call it correctly is missing; the parenthetical clarifies the meaning of a missing calories field.

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% and the single parameter is fully documented in the schema as the restaurant slug from a search response's unique_name field. The description repeats 'by unique_name' but adds no syntax or format detail beyond what the schema already provides, so the 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 (Fetch), a specific resource (one UK Just Eat restaurant's categorized menu items and prices), and the access key (unique_name). It explicitly names what it is not (justeat_search for finding restaurants, justeat_restaurant for store details), so an agent can distinguish it from siblings without opening a schema.

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?

Names the two natural alternatives and the conditions that select them: use justeat_search to find restaurants, justeat_restaurant for store details, leaving this tool for menu retrieval. This is explicit routing with no inference required.

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