Map reachability, across portals

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

With only readOnlyHint available, the description carries the behavioral load and does so richly: blocking requires a same-as-tiles page (isNormalPriority), conditions are not evaluated, standable/touchable/automatic are defined, transfers are followed, and a portal landing on an impassable tile is flagged as a trap. This is exactly the extra context annotations cannot supply.

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-loads the core action and definition, then layers semantics efficiently; nearly every sentence earns its place. It is a dense single paragraph, and the run-on style around the portal/trap clause slightly hurts scannability.

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 traversal tool with no output schema, the description covers reachability categories, transfer following, and the reports ordering well. It omits the entry shape and the maxMaps bound, which are the remaining gaps an agent would want before calling it.

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 only 33%, so the description must compensate. It effectively explains the blocking behavior behind includeEventBlocking and the transfer-following behind followTransfers, but maxMaps (the walk bound) and the coordinate/mapId semantics are never addressed, leaving one non-obvious parameter undocumented.

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: 'flood-fill walkable cells from a start position and report which events the player can actually reach.' It also frames the intent ('can the player get there') versus the naive alternative of trusting tile placement, which cleanly separates it from inspect_cell/get_map siblings.

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 clear context for when to reach for it — verifying actual reachability rather than tile placement, and following portals into destination maps. However, it never names an explicit alternative or exclusion (e.g. when to use inspect_cell instead), so the routing guidance is implied rather than stated.

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