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

With annotations already declaring openWorldHint=true, idempotentHint=false and destructiveHint=false, the description still adds substantial context: hard limits (25 origins, 5 bands, 6 hours, 500 km), the one-unit-per-call rule (MIXED_BUDGET_TYPES), overlap semantics, that analyze counts accounts in every containing area, three named error conditions including quota being checked before the call, and that it returns a task. This is well beyond what the annotations convey.

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 is front-loaded in the first clause, and each subsequent sentence carries distinct information (shapes, limits, semantics, errors). The error-code and quota detail is dense but earns its place for a provider-backed call; the prose is compact given how much is packed in.

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 'Returns a task' suffices for the return value, and the failure modes, limits, and overlap semantics are covered. The remaining gap is the undocumented half of the parameter set, which is not addressed anywhere.

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 0% across 11 parameters, so the description must carry the load. It explains origins, bands, travel_mode (car/truck), and depart_at, but leaves avoid, traffic, route_type, tal_id, tal_label, ts_handle, and map_session_id entirely unexplained in both schema and description. Partial compensation only.

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 ('Draws the area reachable by driving from one or more origins') and names the artifact it produces (a territory in a drive-time alignment). It also disambiguates from nearby siblings like calculate_route and analyze_routes by noting the budget is not route time or territory workload. An agent can distinguish it without opening any 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 explicit conditions and exclusions: realign/split/merge/rebalance return ISOCHRONE_TAL_NOT_EDITABLE, so those tools cannot edit these areas, and it clarifies that a band budget is not territory workload or route time. It never names a positive alternative (e.g., use calculate_route for point-to-point), so it falls short of a full when/when-not/alternative triad.

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