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

With no annotations, the description carries the full behavioral burden and does the most important part: it discloses the credit spend rate (2 per contact), flags it as a mutation that copies contacts into the workspace, and imposes an approval precondition. It does not cover auth requirements, reversibility, or failure/refund behavior, but the critical cost and mutation facts are disclosed.

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?

Three short sentences, front-loaded with the credit-cost warning so the highest-risk fact is read first. Every sentence earns its place; nothing is redundant with the title.

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 one-parameter mutation with no output schema, the description covers the essentials an agent needs: cost, effect on the workspace, and the required preview/approval gate. The only meaningful gap is the undocumented 'id' parameter, but no return-value explanation is needed.

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 0% and the single 'id' parameter is entirely undocumented in both schema and description. The tool name implies it is an audience set id, but the description never names or explains the parameter, so it fails to compensate for the coverage gap.

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?

Specific verb (purchases) plus resource (the audience set) plus concrete effect (snapshots its contacts into the workspace). It also distinguishes itself from the sibling preview_buy_audience_set by casting that tool as the required prior step, so an agent can route between them 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?

States the exact condition that gates invocation: only call after the user reviewed preview_buy_audience_set output and explicitly approved the cost. This is an explicit when-to-use rule with a named prerequisite alternative, not an implied one.

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