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

Beyond the annotations, the description discloses that non-pending rows are refused with 409 and that sent messages cannot be recalled. This adds meaningful behavioral context to the destructiveHint and idempotentHint annotations. It does not contradict any annotation.

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?

Two concise sentences deliver the action, the precondition, and the key error condition without repetition or filler. The most important information is front-loaded.

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 mutation with no output schema, the description covers the valid target state, the invalid states, the error behavior, and the fundamental limitation. Combined with the annotations, an agent has everything needed to invoke 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 coverage is 100% and the single id parameter is already fully described as the scheduled_sms row id from tascan_schedule_sms / tascan_list_scheduled_sms. The description adds no additional parameter-level meaning, so the baseline score of 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?

The description names the exact operation (cancel) and the target resource (a scheduled text/SMS row) and specifies the relevant state (pending). This clearly distinguishes it from scheduling, sending, and generic deletion tools in the sibling list.

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?

It states an explicit precondition — the text must be pending — and explicit forbidden states: sending, sent, failed, or cancelled. It also makes the hard limitation clear with 'a sent text cannot be recalled,' so an agent knows exactly when to use this tool and when not to.

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