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

Annotations already declare readOnly=true, destructive=false, openWorld=false, so the safety profile is covered. The description adds beyond that: the operation is asynchronous and must be polled, a 'waiting' status exists, and score is only populated once the test is completed. It doesn't quantify rate limits or failure modes, keeping it at a strong 4 rather than 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?

Purpose and polling cadence are front-loaded in the first sentence; the remaining two sentences explain the placement/score/rspamd fields compactly. Some of that return-value detail is arguably duplicated by the output schema, but it is readable and not padded.

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-param read tool with an output schema and full annotation coverage, the description carries the load that structured fields cannot: async polling behavior and status semantics. It is essentially complete, missing only explicit mention that testId originates from deliverability_create_test (which the schema does state).

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?

There is a single parameter with 100% schema description coverage, including the format pattern and the pointer back to deliverability_create_test. The description adds no additional parameter meaning, so the baseline 3 for schema-covered params 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 scopes the resource precisely as the per-seed-mailbox placement results of a deliverability test, which an agent can separate from deliverability_create_test by name and by the 'where the email landed' framing. It is slightly output-oriented (describing what the result looks like rather than 'get the test results for testId'), so it stops short of a crisp verb+resource statement.

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?

It gives concrete operational guidance ('Poll about once a minute while status is waiting'), which tells the agent how to consume the async result rather than just what it returns. It never states prerequisites or exclusions, but the sibling create_test is the only natural alternative and no when-not guidance is needed here.

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