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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false). The description usefully discloses that this is an advisory/coordination lock ("so other agents can see this connector is working"), but omits whether locks are enforced, expire, or conflict with existing locks.

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?

A single front-loaded sentence with no padding, and it leads with the action and resource. The trailing clause about other agents is slightly wordy but carries real intent information.

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 6-parameter mutation that has both required and optional fields, the description is thin. An output schema exists so return values needn't be explained, but lock semantics (expiry, conflicts, enforcement) are left unaddressed despite being central to correct invocation.

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 every parameter (paths, reason, message, duration_seconds, etc.) is already documented in the schema. The description adds no parameter-level detail, so the baseline 3 applies.

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 clear verb+resource ("Lock one or more mailbox files") and states the reason (coordination between agents). It does not differentiate itself from the sibling mailbox_lock, so an agent must infer that this targets individual files rather than the whole mailbox.

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 supplies a timing cue ("before editing"), which is genuine usage context, but gives no guidance on when to prefer this over mailbox_lock, how long to hold the lock, or how it pairs with mailbox_unlock_file. Usage is implied rather than specified.

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