Change thread labels / state

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

Annotations already carry the read-only/destructive/idempotent profile. The description adds useful context beyond that: the whole-thread scope, the requirement that at least one change be present, the idempotent behavior that repeated identical changes are harmless, and the return value ('thread's new id and message label state'). No contradiction with annotations.

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?

Three compact sentences with no filler. The action and scope are front-loaded, followed by when to use it, the usage constraint, and the return behavior. Every sentence earns its place.

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?

Despite the lack of an output schema, the description states what is returned. Combined with the fully documented parameter schema and annotations covering safety/idempotence/destructiveness, an agent has everything needed to select and invoke the tool correctly. The only minor gap is alternative-selection wording, which is already addressed in usage guidance.

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% and each parameter already has a detailed description, putting this at baseline 3. The description adds value by enumerating which fields count as 'changes' and by stating the non-schema constraint that at least one change is required. It does not add syntax details, but they are not needed given the schema's completeness.

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 names a precise action — applying the same normalized state changes as modify_message — but scoped to 'EVERY message in a conversation at once'. It lists the exact state dimensions (read/unread, starred, archived, add_label_ids/remove_label_ids), so there is no ambiguity about what the tool operates on.

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 explicitly explains when to use the tool: mark a whole conversation read or archive it in one call instead of looping over messages. It references modify_message as the baseline sibling, but stops short of explicitly saying 'use modify_message for a single message', so it lacks a full when-not statement.

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