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

The only annotation is readOnlyHint=false, so the description carries most of the burden. It does add a real behavioral trait beyond annotations — the slow variant doubles the duration, implying a time cost per move — but it says nothing about whether movement can fail, cost energy/stamina, or be blocked by terrain, which matters for a mutating movement action.

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?

Two short sentences with no filler, and the core action is front-loaded before the parameter note. The dash-separated 'slow' clause is slightly terse but still readable.

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 simple two-parameter movement tool with no output schema and minimal annotations, the description covers the action and the meaning of 'slow'. It leaves out relevant context such as movement cost, failure conditions, and how it relates to faster travel siblings, which an agent would want before choosing 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 description coverage is 0%, so the description must compensate. It does explain 'slow' well (a cautious step taking twice as long), but the required 'direction' parameter is only implied by 'adjacent cell'; the N/NE/... enum is largely self-explanatory, so the gap is moderate rather than critical.

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: 'step into an adjacent cell of the world', which makes clear this is single-tile walking movement. It is not explicitly distinguished from movement-adjacent siblings such as game_portal_escape/game_portal_teleport or game_enter_leave_game_leave_building, but the 'adjacent cell' wording is distinctive enough to separate it from teleport-style tools.

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?

Usage is implied rather than stated: an agent can infer this is the way to move one square, and the 'slow = cautious, takes twice as long' note hints at when the slower option is appropriate. There is no explicit guidance on when to use this versus teleport, enter/leave building, or other movement-adjacent tools, and no prerequisites or exclusions.

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