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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description earns credit for adding return-shape semantics: scheduled_action holds only active work while last_scheduled_action is history, and excluded contacts return state='excluded' with no next_tool. This is meaningful context beyond the annotations, though retry/pagination behavior is not mentioned.

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?

Four dense but front-loaded sentences; the core 'what it does' and the sibling disambiguation come first, followed by return-value detail. Every sentence contributes, though the middle section is tightly packed.

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?

With no output schema, the description compensates thoroughly by describing returned fields (invitation_status values, counts, next_tool, state) and the distinction between active vs historical scheduled actions. An agent has enough to call and interpret the tool correctly.

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 limit (default 50, max 200) and campaign_id fully documented in the schema. The description adds no parameter-level syntax or format detail beyond what the schema provides, so the baseline 3 applies.

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 and resource (see where each campaign contact stands) with enumerated states (invited, accepted, next step), and explicitly disambiguates from the sibling list_campaigns. An agent can distinguish it from list_campaigns without opening either schema.

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?

Names the alternative explicitly ('For campaigns themselves use list_campaigns') and gives the context of inspecting readiness/invitation state contact by contact. Clear routing guidance, though it stops short of a full when/when-not matrix.

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