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

With readOnlyHint and openWorldHint already declaring the safety profile, the description still adds real behavioral context: default best-match ordering that changes only when sort_by is set, and the empty-list behavior for uncovered postcodes. It doesn't cover pagination or result-shape caveats, but the edge cases it does give are valuable.

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?

Three tight sentences: purpose and payload first, then the ordering default and empty-result edge case, then sibling routing. Nothing is padded and the most decision-relevant information is front-loaded.

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 read-only search tool with a full output schema, this covers the essentials: what is returned, the ordering default, the empty-coverage case, and where to go for filters or a single store. Nothing an agent needs to call it correctly is 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 coverage is 100%, so the schema already documents all four parameters in depth (filter OR semantics, sort_by enum, limit clamping). The description only restates the sort_by default, adding little syntax or meaning beyond what the schema carries. 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?

States a specific verb and resource ('Fetch the full Just Eat restaurant listing') scoped to a UK postcode, and enumerates the payload (ratings, images, delivery windows, open status). It also names the sibling tools it is not, so an agent can distinguish it from justeat_restaurant and justeat_search_filters without opening either 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?

The final sentence explicitly routes the agent elsewhere — 'Use justeat_search_filters for accepted filters or justeat_restaurant for one store' — which covers the two nearest alternatives. It stops short of stating an explicit when-not-use condition for this tool itself, but the context is clear.

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