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

Annotations already mark readOnlyHint=false and destructiveHint=false, but the description adds substantial behavioral detail: success returns status 'cancelled', failure produces CAMPAIGN_NOT_CANCELLABLE with the current status, and messages already sent cannot be recalled. This goes well beyond what annotations provide and sets correct expectations.

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 front-loaded with the purpose, then flows logically through conditions, success/error behavior, and alternatives. Every sentence adds essential information with no filler, making it appropriately sized for the tool's complexity.

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 single-parameter tool with no output schema, the description covers the success outcome, the failure mode with error code, the prerequisite condition, and the recommended fallback. Nothing an agent needs to decide whether to call it or to interpret the result is missing.

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 has only one parameter (campaign_id, uuid) with 0% description coverage. The description compensates by telling the agent exactly where to get the ID ('from send_broadcast or list_campaigns'), adding source context that the schema lacks. Since there is only one param, this fully covers its semantics.

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 states a clear verb ('Cancel') and specific resource ('a scheduled broadcast so it never sends'). It also distinguishes from siblings by noting the alternative for in-flight/completed sends (disconnect_whatsapp), so an agent can immediately tell this tool apart without opening other schemas.

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 defines the valid usage window ('only works while the campaign is still scheduled') and states when it cannot be used (started/finished). It names the exact alternative for those cases (disconnect_whatsapp), leaving no ambiguity about selection criteria.

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