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

Annotations already cover readOnly (false) and idempotent (true), but the description adds critical context: consequences (leads can start receiving messages on a running campaign), idempotency (no duplicates), constraints (leads must belong to authenticated account or call fails), and the API key requirement. It enriches beyond annotations without 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?

The description is concise and front-loaded: the first sentence states the core purpose. Each subsequent sentence adds meaningful behavioral or usage context (consequence, non-action, validation, idempotency, verification prerequisite) with zero filler. All within a short paragraph.

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 tool with 3 params and no output schema, the description covers: the operation, limits, consequences, prerequisites, failure conditions, and relationship to other tools (verify_emails, campaign starting). It is remarkably complete for the complexity involved, leaving little ambiguity for the agent.

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%, so baseline is 3 per the rubric. The description adds minimal parameter-level detail beyond the schema (e.g., 'up to 500 at a time' echoes the schema's '1-500', and the note about lead ownership). It does not explain parameter relationships beyond what schema provides, so it stays at baseline.

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?

Description clearly states the action: 'Add saved leads to a campaign's contact list in bulk, up to 500 at a time.' It distinguishes from siblings by explicitly noting it does NOT send or start campaigns, and positions it as the final step before outreach. Specific verb+resource+scope.

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 it ('This is how leads enter an outreach sequence'), what it does not do ('does NOT send anything by itself and does not start the campaign'), and provides a clear prerequisite/recommendation ('Verify addresses with verify_emails first; importing dead ones damages sender reputation'). It even names the alternative tool for verification.

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