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

Annotations declare non-read-only, non-idempotent, non-destructive, but say nothing about the dry-run default or eligibility gate. The description supplies both, including that the default confirm=false performs a dry-run — critical behavior an agent must know before invoking.

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?

Extremely dense: the shell-vs-upload distinction is front-loaded, enum values are inline, and the dry-run hint is last. Every clause carries decision-relevant information with no filler.

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 mutation tool, it covers the dry-run, eligibility prerequisite, and scope boundary; an output schema exists so return values need no explanation. Remaining gaps are the meaning of membership_days and which account customer_id refers to.

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% across 5 params, so the description must compensate. It documents upload_key_type's allowed values and confirm's dry-run meaning, but leaves name, customer_id, and membership_days (540-day default) unexplained.

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 and resource ('creates an EMPTY list shell' for a Customer Match audience), and the word EMPTY plus 'this tool only creates the list' distinguishes it from audience-creation siblings that also populate membership.

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 context: member upload is a separate step requiring Customer Match eligibility, and confirm=false yields a dry-run. It does not name a specific alternative tool for the upload step or for other audience types, so it falls just short of explicit routing.

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