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

Annotations provide readOnlyHint=false, destructiveHint=true, idempotentHint=true. The description adds substantial behavioral details beyond annotations: suppression-safe importing, return of removed counts, pausing active campaigns, human confirmation requirement, 5,000 recipient limit, and dry_run behavior. No contradiction with 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?

Three sentences, front-loaded with the primary action, then return behavior, side effects, limit, and dry_run. No filler; each sentence adds distinct 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?

The description covers core behavior, dry_run semantics, and limits, but omits explanations for confirmation_token and finalize_incomplete. It also only partially describes the return (removed counts) without a full response structure. Given 6 parameters and no output schema, this is incomplete.

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 only 17% (only idempotency_key has a description). The description explicitly explains dry_run's behavior ('dry_run: true returns an advisory estimate...') and the recipient maximum (5,000), which relates to the leads parameter. However, it does not explain confirmation_token or finalize_incomplete, which remain undocumented. Given low schema coverage, the description should compensate more.

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 action: 'Add recipients to a draft or incomplete campaign' with a specific method ('suppression-safe bulk importer'). It distinguishes itself from sibling tools by specifying the campaign state (draft or incomplete) and the return of removed counts, making it clear this is for bulk addition to non-active campaigns.

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 explicitly states the condition for use: 'Add recipients to a draft or incomplete campaign' and warns about the side effect on active campaigns ('pauses it and requires signed-in human confirmation'). This gives clear when-to-use guidance, though it doesn't explicitly name alternative tools for active campaigns.

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