Change message labels / state

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

The annotations mark destructiveHint=true, while the description asserts 'This never deletes anything — use manage_trash for the trash.' This categorical non-deletion claim conflicts with the machine-readable destructive hint, creating an inconsistent safety profile. The description adds useful detail (idempotence, return value), but per rubric any contradiction with annotations scores 1.

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?

The description is front-loaded with the core action and parameter summary, then proceeds to constraints, safety, sibling routing, and return value. Every sentence adds information; there is no filler or duplication of the schema beyond what helps clarity.

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 mutating tool with no output schema, the description covers what the agent must know: parameter effects, required-change condition, idempotency, safety boundary, and the return shape (new id/labelIds). Minor omissions like explicit error behavior when no change is supplied are acceptable because the constraint is stated.

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 baseline is 3. The description adds value beyond the schema by stating the cross-parameter invariant 'At least one change is required,' explaining idempotence, and giving concrete examples of label ids (IMPORTANT, Label_123). This pushes it above baseline.

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 opening line 'Changes a message's state via Gmail labels' names a specific verb and resource, and the body enumerates the exact state transitions (read, starred, archived, add/remove labels). It also distinguishes itself from the sibling manage_trash by explicitly stating 'This never deletes anything — use manage_trash for the trash.'

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 invocation guidance: at least one change is required, duplicate changes are harmless, and trash-related operations should go to manage_trash. It doesn't explicitly contrast with modify_thread or other state-changing siblings, so it isn't a full when-to-use map but is sufficiently clear for most routing.

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