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

With no annotations provided, the description carries the full burden of behavioral disclosure. It clearly states the tool reads stored data (non-mutating) and explicitly discloses that the data may be stale ('returns what was stored at the last observation'), implying that 'verify' is the action that refreshes it. This is valuable context beyond the schema.

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 two concise sentences with zero waste. It front-loads the purpose ('Read one stored sending-domain resource') and adds the key nuance about staleness and the alternative in the second sentence. No redundant phrasing.

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 single-resource read with two parameters and no output schema, the description adequately explains the core behavior and the main alternative. It doesn't detail the response format, but that is not required given the simplicity and the absence of an output schema. The description is sufficient for an agent to decide when and how to call it.

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% for both required parameters (domain_id and organization_id), so the schema already documents them adequately. The description adds no additional parameter-level detail, which is acceptable given the high coverage; the baseline of 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?

The description states a specific verb ('Read') and resource ('one stored sending-domain resource'), and distinguishes it from the 'verify' sibling by clarifying that it returns the last observation rather than a fresh check. The singular 'one' differentiates it from plural list tools like 'domains'.

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 explicitly names the alternative 'verify' and the condition under which to use it ('To look again, call verify'), which gives clear guidance for the most relevant sibling. It does not enumerate other domain tools, but those serve different purposes (report, deliveries, smoke), so the key distinction is covered.

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