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

Annotations already declare readOnly/openWorld=false, and the description adds substantial behavior beyond them: newest-first ordering, pagination via cursor/nextCursor with null terminator, UTC interpretation of offsetless dates, inclusive date-only `to` versus exact timestamp `to`, and even the domain rule that airside connections stay one journey while airport exits split journeys. The output-field naming difference between read (`departureAt`) and write (`departureDate`) inputs is exactly the kind of non-obvious detail an agent would otherwise get wrong.

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, ordering and filters are front-loaded, and most sentences carry non-obvious information. A couple of clauses (the leg-time versus write-input naming, the domestic-journey day-count note) are only tangentially needed to invoke this read tool, which keeps it from a 5.

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-field enumeration is unnecessary — yet the description still explains pagination contract and the newest-first ordering an agent needs to page correctly. Combined with the date-semantics and guide pointer, nothing material for a correct call 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 baseline is 3, but the description adds real semantics on top: the cursor must come from a prior response's `nextCursor`, and `to`/`from` interpretation differs for date-only versus full-timestamp values (whole UTC day versus exact instant). It also defines what a journey is for filtering purposes (airside vs split journeys, domestic journeys valid but excluded from day counts).

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 ("List the user's journeys") and immediately qualifies the domain object ("movements between countries") plus what is returned (presence stamps, ordered legs, newest-first). This clearly distinguishes it from get_journey (single journey), list_stays, and detect_journey_gaps without needing the 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?

Gives a concrete routing hint: "If unfamiliar with TripLedger semantics, call get_tripledger_guide first," and explains that filters are optional. It does not state when to prefer this over siblings like list_stays or get_travel_summary, so an explicit exclusion is missing, 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.