Check an e-invoice against EN 16931

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, and the description is consistent with these. It adds valuable context beyond the annotations: the file is uploaded over HTTPS, processed in memory and discarded, requires FACTUROLIA_API_KEY, has a 10 MB limit, and is rate limited per key tier. It also clarifies that the tool does not transmit invoices to any tax platform.

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 dense but each sentence earns its place: what it returns, when to use it, what it excludes, and what side effects/limits apply. There is no redundancy, and the most decision-relevant content is front-loaded.

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?

With no output schema, the description compensates by specifying exactly what is returned: the verdict and a list of anomalies with rule codes and figures. It also covers formats, constraints, authentication, limits, and side effects. For a one-parameter validation tool, nothing essential is missing.

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%, so the input schema already documents the single 'path' parameter clearly, including accepted file types. The description reinforces the file-format context but does not add meaningfully new parameter-level semantics beyond the schema. Baseline 3 is appropriate.

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 ('Validate') and a precise resource ('electronic invoice file against EN 16931'), and enumerates supported formats. It also distinguishes itself from the sibling read_invoice by explicitly saying it does not list invoice contents. An agent can clearly tell what this tool does and how it differs from the alternative.

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 gives explicit use cases: answer 'is this invoice correct?' or screen several files quickly. It also names the alternative read_invoice for content-related questions and clarifies what this tool is not (not a legal compliance certificate, not a tax submission). This leaves little to inference.

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