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

With no annotations, the description carries the burden and does well: it discloses the key non-obvious behavior that parsing runs in the background requiring a poll, and the billing consequence (no credits for this call). It omits the failure/error behavior and permission requirements, keeping it from a 5.

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 tightly packed sentences, front-loaded with the core action and follow-up operational facts. Every sentence earns its place with no redundancy.

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 creation tool with no annotations and no output schema, the description supplies the critical async/polling and credit-model context an agent needs to invoke it correctly. Remaining details (column mapping sourcing, size limits) are adequately covered by the schema.

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%, so the baseline is 3. The description reinforces file formats and the two input methods but adds no syntax or constraints beyond what the schema already documents; the schema, not the description, carries column_mapping and size limits.

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 specific verb (Create) and resource (custom audience) scoped to file ingestion, and lists the accepted formats (CSV/XLSX/XLS/TSV/TXT) plus both input methods (base64 or https URL). It does not explicitly differentiate from the sibling create_custom_audience, so it falls just short of a 5.

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 operational context: parsing is asynchronous, so the agent should poll get_custom_audience until status is 'ready', and it clarifies the credit model (no credits here, enrichment is separate/paid). It lacks an explicit comparison to create_custom_audience or preview_custom_audience_file, so no exclusion guidance.

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