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

Annotations only declare it is a write (readOnlyHint=false), open-world, non-destructive. The description adds genuinely non-structured behavior: billing only on customer response, charge drawn from the payment method rather than the weekly budget, failure on closed Opportunities, per-call confirmation default, and the required Cotlet API key scope. This is exactly the value structured fields cannot 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?

Front-loaded and readable, but the charging rule is stated twice in near-identical wording ('You are charged only if the customer responds' and 'charges ... only if the customer responds'), and the opening restates the title. The repetition costs it a point.

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 covers the behaviors an agent needs: cost model, budget interaction, closed-opportunity failure, confirmation default, human-approval duty, and API key prerequisite. Nothing material for correct invocation 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 description coverage is 100%, so all three parameters (body, quote_price, opportunity_id) are already documented in the schema, including that opportunity_id comes from list_opportunities and quote_price is optional. The description adds no syntax, format, or constraint beyond that, so 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 concrete verb and resource ('Message an Opportunity with an optional quote') and scopes it to exactly one Opportunity, which separates it from siblings like thumbtack_send_message or thumbtack_list_opportunities. The agent can tell what it does without opening the 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?

Gives clear operating context: cost is cited from list_opportunities, the call fails if the Opportunity has closed, and confirmation is on by default. It does not explicitly name a competing sibling (e.g. send_estimate vs this tool) as the alternative, so it stops short of full when/when-not routing.

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