modify_labels

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

Discloses side effects: changes the thread's labels; reversible by inverse call. Complements annotations (idempotentHint=true, destructiveHint=false) with useful context. No contradiction.

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 sentences, front-loaded with purpose. Efficient, though could be slightly more condensed. No redundant information.

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 (modify labels), presence of output schema, and sibling tools, the description is complete. Covers usage, side effects, and alternatives.

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 0%, so description must compensate. It gives examples (archive, mark read) but does not explicitly state that add/remove take label IDs. Adequate but not rich.

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?

Clear verb+resource: 'Add/remove labels on a thread.' Explains special label mappings (archive=remove INBOX, mark read=remove UNREAD). Distinguishes from sibling tools like archive and mark_read.

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?

Explicitly states when to use ('applying custom labels or label combinations in one call') and when NOT to use ('plain archive/read/unread — the dedicated tools are clearer'). Also mentions side effects.

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