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

Annotations already establish readOnly/safe behavior, but the description adds substantial behavior beyond them: deduplication of cities, first-seen order preservation, the 20-destination cap, empty-state rendering, the same-locale constraint, and the warning not to recreate the component as a carousel/grid/list/table.

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, invocation constraint, and the sibling routing are front-loaded, with the dedup/cap/empty-state and rendering rules following. Dense but every sentence carries operational information; only minor trimming is possible.

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?

An output schema exists, so return values needn't be explained, and the description covers the ordering, dedup, cap, empty-state, locale, and single-render constraints an agent needs to invoke it correctly.

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 param is fully documented in the schema, so the baseline is 3. The description adds meaningful semantics beyond it: results must be passed unchanged, kept in combined order, and share the same locale even when filters/pages/limits differ.

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 (Render) and resource (destination widget) and explicitly distinguishes itself from the sibling discover_destinations by positioning itself as the final step after those calls complete. An agent can tell the two apart 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?

Explicitly names the prerequisite sibling ('after all discover_destinations calls are complete'), the invocation count ('call this tool exactly once'), and the ordering of results. This is unambiguous when/when-not guidance.

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