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

Goes well past the annotations (readOnlyHint=false, idempotentHint=true): it states what Mappu does NOT do (generate, book, charge), that it stores the plan as given and matches stops to real places only after the traveler keeps it, and it discloses the return contract — a link to a draft that expires after 7 days, or a saved-trip link with a connected account.

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?

Front-loaded with the action, and most sentences carry distinct information (trigger, prerequisite, payload shape, return value, idempotency). It is dense and runs long for a single paragraph, with some content that overlaps the schema, but the length is defensible for an 8-parameter nested payload.

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 complex write tool with nested days/stops and no output schema, the description covers the return values (draft link with 7-day expiry, saved-trip link), the non-actions (no booking/charging), and the retry semantics. An agent has everything needed to call 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%, so the baseline is 3, but the description adds aggregate composition guidance the per-field schema does not: send the plan whole with each day's theme and ordered stops with start times, descriptions, tips, food and practical tips. The idempotencyKey retry note largely restates the schema, so it is not a full 5.

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 ('Save a trip plan... into Mappu') and immediately characterizes the artifact Mappu keeps ('day-by-day itineraries on a map'). It is clearly distinguishable from siblings like mappu_get_trip_planning_guide and mappu_find_walks, which the description explicitly positions against.

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 an explicit trigger ('Use this tool when the traveler wants to keep the plan you agreed on'), a prerequisite step ('Before planning, read mappu_get_trip_planning_guide'), and a negative rule ('Mappu's walks and audio guides are extras, never a day's outline'). Alternatives and exclusions are named rather than implied.

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