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

Beyond the annotations (idempotentHint=true), the description discloses crucial behaviors: duplicates are silently skipped, maximum domain counts per account and per request, subdomain coverage, and rejection of non-registrable formats. This goes well beyond what annotations provide and prepares the agent for expected outcomes.

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?

The description is concise (five sentences) and front-loaded with the main action. Each sentence adds distinctive value: purpose, scoring effect, format rules, subdomain behavior, and limits. No fluff or 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 simple one-parameter add tool with no output schema, the description is fully adequate. It covers what the tool does, when to use it (scoring context), format constraints, limits, and edge-case handling (duplicates, subdomains). No critical gaps remain for the agent to select and invoke correctly.

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?

Although the schema already describes the 'domains' parameter with 100% coverage, the description adds significant nuance: registrable domain only, subdomains automatically covered, and per-request limit of 100. This extra information is essential for correct invocation and was not fully captured in the schema description.

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 'Add one or more domains to this account's trusted allowlist,' using a specific verb and resource. It clearly distinguishes from sibling tools like list_allowlist and remove_from_allowlist by stating the add action and the domain format requirements.

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?

The description provides clear context by explaining the effect of allowlisting (suppresses compound signal and brand impersonation floor) and that the full pipeline still runs. It does not explicitly name alternatives or exclude when not to use, but the purpose is unambiguous given the sibling names.

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