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

Annotations declare readOnlyHint=false and destructiveHint=false, indicating a non-read-only but non-destructive write. The description adds that it adds all segment contacts as recipients, giving some behavioral detail. However, it does not disclose potential ambiguity about existing recipients or side effects, so the added transparency is limited beyond the 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?

Two sentences with zero waste: the first states the action and effect, the second provides usage context. Front-loaded and efficiently structured.

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?

For a simple mutation tool with 3 fully-described parameters and no output schema, the description covers purpose, effect, and usage context well. It lacks edge case disclosures (e.g., overwriting behavior) but is complete enough for the complexity level.

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%, with all three parameters having clear descriptions (segment_id, campaign_id, campaign_type). The tool description does not add additional parametric meaning beyond the schema, so baseline 3 is appropriate.

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 uses a specific verb 'Apply' and resource 'saved segment to existing campaign draft', and clarifies the outcome by adding all segment contacts as recipients. It distinguishes from sibling tools by focusing on the segment-to-campaign application, not generic contact addition or campaign creation.

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 'Use after list_segments when user picks a segment to add to a draft,' providing clear timing and context. However, it does not mention alternatives or when not to use, which keeps it from a perfect score.

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