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

Adds key behavioral context beyond annotations: 'It starts sending as soon as the worker picks it up' and 'Sending speed defaults are conservative on purpose.' This tells the agent the tool has immediate side effects and that altering speed params is discouraged. Annotations already cover read-only/destructive hints, so the description complements them.

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, each with a distinct purpose: what it does, the confirmation requirement, and placeholder/speed guidance. No filler or repetition of schema details.

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 13-parameter tool with no output schema, the description covers the critical behavioral and safety aspects (immediate sending, confirmation, speed defaults). It doesn't explain return values or what happens on duplicate calls, but idempotentHint=false already signals non-idempotency. Missing a bit of detail on follow-ups/lead_filter, but schema covers those.

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 100%, so baseline is 3. The description adds extra value by specifying placeholder syntax ('{{first_name}}, {{company}}') and by warning that speed defaults are intentionally conservative, which informs how to treat daily_limit, hourly_limit, and delay params. This goes beyond the schema's per-param 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?

States a specific verb+resource: 'Queue a cold email campaign against a lead list.' It also clarifies the scope (cold email, lead list) and distinguishes from siblings like create_list or control_campaign by emphasizing the immediate start of sending.

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?

Provides explicit when-to-use guidance: get user agreement on subject, body, and audience size before calling. Also warns not to raise sending speed defaults unless asked. However, it doesn't name alternative tools for related actions (e.g., control_campaign for pausing), so it's not a full routing guide.

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