label_thread

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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=false. The description adds useful behavioral context beyond that: labels are applied to every message in the thread, and a folder label moves the conversation. It does not cover permissions or return behavior, but with annotations present the bar is lower.

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 wasted wording. The key scope, thread-wide labeling, and a representative example are communicated immediately.

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?

The tool is simple, has only two required parameters, no output schema, and annotations that cover safety and idempotency. The description is nearly complete for correct invocation, missing only explicit sibling-routing guidance, which is a minor gap.

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 50%: labelIds is richly documented with valid values and folder-move semantics, while threadId has no schema description. The description adds examples such as STARRED and folder labels, but does not add meaning beyond what the labelIds schema already provides. Baseline 3 is appropriate for this coverage level.

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 states a specific verb and resource: "Adds labels to every message in a thread." This clearly distinguishes thread-level labeling from message-level siblings like label_message, though it does not explicitly name alternatives. The examples (STARRED, folder label) further sharpen the operation.

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?

Usage is implied by the thread-level scope and folder-label example, but there is no explicit guidance on when to choose this over label_message, update_message_labels, or unlabel_thread. The agent must infer the alternative from the sibling names.

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