apply_label

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

With zero annotations, the description carries the burden and does disclose the key hidden trait: this mutates inbox state by archiving, and the change is reversible. It omits residual behavior an agent might want (whether label_id must pre-exist from list_labels, what happens on unknown ids, and the response shape), which keeps it below a 5.

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?

Two tight sentences: the compound action and its reversibility first, then the usage gate. Nothing is redundant or buried.

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 two-parameter mutation tool with no annotations and no output schema, the description covers the side effect and the when-to-use rule but leaves parameters and return behavior entirely undocumented. It is adequate but has clear gaps.

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% for both required parameters, so nothing in the structured data explains them. The description adds no meaning at all about message_id or label_id — notably it never says label_id must come from list_labels, which is the main failure mode.

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 (label) plus a non-obvious second effect (archive out of the inbox), which distinguishes it from the name alone. It is clearly separable from read-oriented siblings like get_message and search_messages, though it does not explicitly reference them.

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?

Gives an explicit gating condition: call only for high-confidence classifications, and leave unsure messages in the inbox. It does not name an alternative action for the low-confidence case (e.g., label without archiving, or just read with get_message).

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