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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and determinism are covered structurally. The description contributes the substantive behavior that matters — the closed-corpus constraint ('answer only from what this returns') and the phone-number fallback. It does not describe error behavior for an unknown tour slug, so it adds value but not rich context beyond annotations.

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 sentences, front-loaded with the payload inventory, then usage intents, then the grounding constraint. The field enumeration is long but each item is a distinct answerable topic an agent would otherwise have to guess at. Little waste.

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?

With no output schema and a single parameter, the description carries the full burden of describing the return payload, and it does so by naming each content section. Combined with the grounding rule and the fallback path, an agent has everything needed to call it and to handle an incomplete answer.

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 already explains that 'tour' takes a slug from search_tours.tour_id or an exact name, including an example. The description adds nothing about the parameter, so the schema does all the work and 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?

Opens with a specific verb+resource ('Full details for one tour') and enumerates exactly what comes back — description, stops, meeting spot with map link, duration, difficulty, FAQ, policies, rating. That makes it clearly distinguishable from search_tours by scope (one tour vs. search results), though the description itself never names the sibling tools; the linkage appears only in the schema's reference to search_tours.tour_id.

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?

Gives concrete example intents ('how much walking is it?', 'can kids come?', 'where do we meet?') that map directly onto the returned fields, and adds an explicit exclusion/fallback: answer only from what this returns, otherwise give the phone number. This tells the agent both when to use it and what to do when it is insufficient.

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