bulk_update_flags

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

Annotations only provide destructiveHint: false. The description adds valuable behavioral context: it discloses that the operation modifies flags, and importantly reveals the return behavior 'Returns notApplied[] per message for flags the server silently dropped.' This goes beyond the sparse annotation, though it does not mention potential side effects like runaway operations (covered in schema) or permission requirements.

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 four sentences, each purposeful: purpose, usage, input constraints, and alternative. It is front-loaded with the main action and provides critical details without redundancy.

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 tool's complexity (7 params, nested match object, no output schema), the description covers essential context: batch operation, XOR input modes, return behavior, and when to prefer the single-message alternative. It does not address edge cases like empty flag arrays or conflicting flagsToAdd/Remove, but it provides a solid operational picture.

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 high (86%), so baseline is 3. The description adds key parameter semantics beyond the schema, notably the XOR relationship: 'Accepts emailIds[] OR match+folder (XOR).' It also clarifies flag format with an example. This adds meaning that is not obvious from individual schema descriptions.

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 tool's function: 'Add or remove IMAP flags on multiple messages simultaneously.' It specifies the resource (IMAP flags) and the scope (multiple messages), and distinguishes itself from sibling tools like update_message_flags by emphasizing batch operations and the XOR input mode.

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 gives explicit usage context: 'Use when the same flag change... should apply to several messages' and provides an explicit alternative: 'Prefer update_message_flags for a single message when you need per-flag server verification.' This clearly guides tool selection.

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