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

Adds substantial behavior beyond the annotations (readOnly=false, destructive=false, openWorld=true): the invoice number becomes fixed, status flips to open, sending is final, and if 'enshrine on finishing' is enabled the invoice can no longer be edited. It also discloses confirmation behavior and the required API-key scope. This is exactly the mutation/irreversibility context an agent needs.

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 core action, then behavioral caveats and auth requirements. Slightly redundant in restating 'finishes the invoice and sends it by email' after the opening sentence, but every sentence carries usable information.

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 6-parameter mutation tool with no output schema, the description covers purpose, format options, irreversibility, confirmation policy, and auth scope — everything needed to invoke it safely and correctly.

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 already 100%, so the baseline is 3, but the description goes further by explaining the format enum semantics in detail (zugferd_pdf embeds XML in the PDF; xrechnung_xml sends XML only). That distinction is not in the terse schema enum description and materially aids correct selection.

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 precise compound action (finish a draft invoice and email it) on a specific resource, and distinguishes itself from siblings like sevdesk_create_invoice_draft by emphasizing that it both finalizes and sends. An agent can tell exactly what this does without opening the schema.

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 clear context for use: it operates on a draft invoice, requires user confirmation before each call by default, and reaches other people. It doesn't explicitly name a competing sibling (e.g., sevdesk_mark_invoice_paid), but the when-to-use condition is clear and unambiguous.

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