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

With only readOnlyHint=false in annotations, the description carries the behavioral burden and does so well: it discloses that Atlas rechecks the lock server-side, that a LOCKED room writes no stamp and grants no authority, and that an OPEN room appends a stamp and scopes you to that single room. It does not describe the response shape or any rate/idempotency behavior.

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?

Three tight sentences plus a bracketed gate, front-loaded with the admission prerequisite and then the two outcome branches. Every sentence carries operational meaning with no filler.

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 mutation tool with no output schema, it covers the key success/failure branches and the admission precondition. Domain terms ('stamp', 'declaration', 'authority') are used without definition, which slightly limits completeness, but the agent has enough to invoke 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 description coverage is 100%, so all three parameters (room_id, matter_id, actor_token) are already documented, including the optional-when-single-matter rule. The description adds no parameter-level syntax or format detail beyond implying the admission prerequisite, so the baseline 3 is appropriate.

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?

The description gives a specific verb and resource: 'Cross one room threshold,' making clear this is the room-entry operation. It distinguishes the entry case ('places you inside that room only'), but never names the contrasting siblings such as atlas.leave_room or atlas.request_room_access, so sibling differentiation is left implicit.

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?

It states a concrete prerequisite chain ('[NEEDS ADMISSION: enroll, then atlas.bind_actor]') and the conditions under which the call succeeds vs fails (OPEN vs LOCKED room). It stops short of routing the agent to alternatives when admission is missing (e.g., request_room_access) or when the room is locked.

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