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

With no annotations, the description carries the full burden. It does disclose an auth requirement ('needs the results:read scope') and confirms the call is a read, but says nothing about rate limits, whether results may still be pending/in-progress, or pagination behavior.

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?

Front-loaded with the primary action in the first clause, and no padding sentences. The trailing clause 'which reaches the same job when it was itself submitted by that session' is slightly convoluted but does convey the equivalence of the two credential paths.

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?

There is no output schema and no annotations, so the description is the only source of behavioral context. It covers purpose and credential handling but leaves the shape of 'results' (status, terminal vs. pending states) unstated for a tool whose output is the whole point.

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 both parameters are already fully documented in the schema (including the read-only/no-token-billing note). The description restates the api_key dual-mode behavior but adds little beyond what the schema text already provides, so baseline 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?

States a specific verb+resource+key: 'Fetch a verification job and its results by job UUID.' This clearly separates it from siblings like list_jobs (enumeration), verify_email (submission), and get_batch_results (batch-scoped).

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?

Explains the two credential modes for reaching the job (pass the owning api_key vs. omit and use session scope) and names the required scope. However it doesn't contrast with sibling tools such as list_jobs or verify_email, so the when-to-use-this-vs-alternatives dimension is only partly covered.

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