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

Goes beyond the readOnly/idempotent annotations by disclosing the key behavioral trait: it does not submit or count another document, so calls are free of quota impact. It also previews the payload (spreadsheet links, math check, extracted data), which is valuable given there is no output 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?

Three sentences, front-loaded with what it returns and keyed on the job_id, then the no-double-count guarantee, then the usage rule. No filler or redundant restatement of the title.

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 single-parameter read tool with full annotations and no output schema, nothing an agent needs is missing: source of the id, return contents, and side-effect/quota behavior are all covered.

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% and the parameter is a simple job_id, so the baseline is 3. The description adds real meaning by noting the id may come from any reader and that a still-processing reader's job_id is also valid.

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 ("Retrieve an already submitted invoice by the job_id") and scopes it precisely to results of prior submissions. It is clearly distinguishable from the sibling extractors/converters, which submit work rather than fetch outputs.

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 an explicit routing rule: use this for additional outputs from the same invoice instead of calling another reader with the file again. It stops short of naming specific siblings or stating the boundary case (when to submit fresh instead), but the when-to-use condition is unambiguous.

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