bulk_update_labels

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

Annotations indicate non-read-only, non-destructive, idempotent. The description adds behavioral context: label paths must start with 'Labels/', dryRun allows safe preview, and removing a label not on a message is a silent no-op (from labelsToRemove description). This adds value beyond 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?

The main description is two sentences, extremely concise and front-loaded. It states the purpose first, then constraints. There is no wasted text, and 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?

Given the complexity (6 parameters, nested match object, XOR requirement), the description covers the essentials: what it does, constraints, safety preview, and reference to sibling tool for label-path rules. No output schema is present, but the return value is implied for dryRun. Missing error scenarios, but not critical.

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 100%. The description summarizes the mutual exclusivity and minimum requirements, and each parameter field has detailed descriptions that add meaning beyond the schema (e.g., folder 'Messages stay here; labels are additive', match conditions, labelsToAdd requirement to exist, labelsToRemove silent no-op, dryRun preview). The description effectively compensates for any complexity.

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 clearly states the operation: 'Add or remove Proton labels on many messages in one operation.' It specifies the verb (add/remove), the resource (labels on messages), and the scope (bulk). This distinguishes it from siblings like update_message_labels (single message) and bulk_update_flags (different 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?

The description provides explicit usage guidance: 'Provide EITHER `uids` OR `match` (XOR), plus at least one of `labelsToAdd` / `labelsToRemove`.' It also references sibling tool `update_message_labels` for label-path rules and suggests `dryRun: true` for safe preview. While not explicitly stating when NOT to use it, the context is clear enough.

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