Export issued invoice (PDF / ISDOC)

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real context on top: the call writes a file to the machine running uol-mcp, a side effect not captured by readOnlyHint. It also discloses that ISDOC output is XML readable line by line and that the format is only available for confirmed issued invoices.

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 short sentences, front-loaded with the core action and file-write behavior, followed by the format variant and the eligibility restriction. No filler or repetition 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?

With an output schema present, return-shape explanation is unnecessary, and the description covers the action, the format option, and the invoice-type restriction. A minor gap is any hint about where the saved file lands or how the caller learns the path, which is left entirely to the output schema.

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 50% — invoice_id is documented in the schema, format is not — but the description compensates by explaining what format=isdoc actually yields (Czech e-invoice XML, line-by-line readable) rather than just restating the enum. The default of pdf is only implied by the schema, not discussed.

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: 'Downloads an issued (sales) invoice rendered by UOL and saves it on the machine running uol-mcp,' plus the format=isdoc variant. This distinguishes export-to-file from metadata retrieval siblings like get_sales_invoice, though it never names that sibling explicitly.

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 exclusion: 'ISDOC exists only for issued (confirmed) invoices' and 'Received invoices cannot be exported through the API,' which steers agents away from using it on purchase invoices. It stops short of naming an alternative tool for received invoices or explaining when PDF should be preferred over ISDOC.

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