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

Annotations declare destructive and idempotent but say nothing about the actual guardrails; the description adds three behaviors an agent could not otherwise know: refusal of ai_send_block and ai_protected labels in both directions, mutex-group replacement with mutex_removed reporting, and optimistic concurrency via expected_version.

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?

Four short sentences, each delivering distinct information with the core action front-loaded and the constraints following. Nothing is repetitive or padded.

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 mutating, version-guarded tool with an output schema (which covers mutex_removed), the description supplies the permissions/refusal rules, concurrency contract, and side-effect reporting an agent needs to call it safely. Nothing essential is missing.

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% across 5 parameters, so the description must carry the load. It explains expected_version's meaning and where to obtain it, and implies add/remove are label identifiers on the stated target types; it does not clarify target_id's numeric-string form or the 20-item caps, leaving a modest gap.

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 opens with a specific verb pair and resource ('Add and/or remove labels') and scopes it to both 'conversation or contact', which no sibling tool covers. An agent can distinguish this from create_label or list_labels immediately.

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 gives clear operational context: pass expected_version sourced from get_conversation / get_contact for conflict-safe updates, and protected labels will be refused. It does not explicitly name alternatives such as list_labels for discovering label IDs, but the when-to-use condition is unambiguous.

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