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

Annotations only mark non-readOnly/non-idempotent/non-destructive, which is relatively uninformative. The description adds real behavioral detail: it compares agent messages with stored history, stores new messages as a side effect, and runs AI crafting plus lead-intent detection. This goes well beyond what the annotations convey.

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 tightly packed sentences with no filler; the main purpose and primary differentiator are front-loaded, and the sibling routing is stated at the end. Every sentence adds 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?

For a no-parameter tool with no output schema, it covers the workflow, side effects, intent detection, and where to use it. The one gap is that the return value (crafted reply and/or intent classification) is implied rather than explicitly stated.

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?

The input schema has zero parameters and 100% schema coverage, so the baseline is 4. The description explains the data flow ('agent-provided messages', 'stored history') despite no schema fields, though it leaves slightly unclear how messages are supplied to a tool with an empty input schema.

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 opens with a specific verb and resource ('Generate a contextual follow-up message') and explains the underlying process. It explicitly differentiates from campaignstack_craft_message for first-contact messages, so an agent can tell them apart immediately.

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 clear routing guidance: 'Use for any message where prior conversation exists' and explicitly directs first messages to campaignstack_craft_message. This leaves no ambiguity about when this tool is appropriate.

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