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

Annotations already declare the safety profile (readOnly=false, idempotent=true, destructive=false), so the bar is lower. The description nonetheless adds a genuinely useful behavioral constraint not present in the structured data: only locks held by this MCP connector can be released, which tells the agent this call will not free another client's lock.

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 filler; the scope qualifier ('locked by this MCP connector') is attached directly to the action it modifies. Nothing in it is redundant with the name or 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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. What is missing is failure behavior — what happens when the file is not locked, or the lock belongs to another connector — which matters for a tool whose whole purpose is conditional on lock ownership.

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%, including a documented mailbox-relative path format and the optional reason/account_id semantics, so the schema carries the parameter burden. The description adds no syntax, format, or defaulting detail beyond what the schema already provides, making the baseline 3 correct.

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 (Unlock) and resource (a mailbox file), which is clearly narrower than the sibling mailbox_unlock. However, it never names or contrasts with mailbox_unlock or mailbox_lock_files, so the agent must infer the distinction from the resource noun alone.

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?

There is no explicit when-to-use statement, no prerequisites, and no reference to the alternative tools mailbox_unlock or mailbox_lock_files. The only implied constraint is that the lock must have been taken by this connector, which is stated as scope rather than as guidance.

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