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

Annotations already declare the mutation and idempotency profile, and the description adds genuinely new behavior: a version precondition that produces a conflict rather than an overwrite. That is exactly the kind of non-obvious failure mode an agent needs. It is weakened only by the vague "keep values small" (no actual size ceiling) and by not saying what a successful write returns.

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 short sentences, front-loaded with the action and the most failure-prone detail (the version precondition) before the soft guidance. No padding or restated title.

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 five-parameter write tool with no output schema, the description covers the risky path (concurrent writes) but not the success path — an agent running a read-modify-write loop is not told that the new version comes back and must inspect the response. That is a real but narrow gap in an otherwise complete definition.

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 meaning the schema does not: if_version is framed as "the version you read," turning a bare number field into an optimistic-concurrency workflow with a defined failure outcome. The remaining params are left entirely to the schema, which is acceptable at full coverage.

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?

"Set one key in the room's shared memory" gives a specific verb plus resource and scope (one key, room-scoped), which separates it cleanly from room_memory_get and room_memory_delete. It stops short of naming the nearest siblings (room_artifact_put, room_playbook_set) that also write room-scoped state, so the agent must infer which store is right.

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?

The description gives concrete operational guidance for the if_version path (pass the version you read, otherwise you get a conflict) and a soft value-quality rule. It never states when to choose this tool over room_playbook_set, room_artifact_put, or room_memory_delete, so selection guidance is only implied.

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