Update Fortnox Invoice

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

Annotations already provide readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds meaningful behavioral context beyond these: the unbooked precondition and that the rows parameter replaces all existing rows. This is important side-effect information not captured by the annotations.

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 compact and well-structured: a one-sentence purpose, a succinct Args list, and a Returns line. Every sentence earns its place, and the 'Other fields: Same as create_invoice' shorthand avoids lengthy repetition.

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?

Given the 11-parameter schema, 100% schema coverage, and presence of annotations, the description covers the essential context: it mentions the unbooked restriction, the row-replacement behavior, and the return value. It relies on the sibling create_invoice for field semantics, which is acceptable but not fully self-contained.

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?

The schema description coverage is 100%, so all 11 parameters are already documented with meaning and constraints. The description restates document_number as required and says rows replaces all existing rows, but both are already present in the schema. 'Other fields: Same as create_invoice' is a minor cross-reference but does not add per-parameter semantics.

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 clearly states the action ('Update an existing invoice in Fortnox') and identifies the specific resource (existing invoice). It also includes a key scope constraint ('Only unbooked invoices can be updated') that distinguishes it from create_invoice and other invoice operations.

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 provides clear context: this tool is for updating existing unbooked invoices, and explicitly warns that booked invoices cannot be updated. However, it does not explicitly name alternatives (e.g., 'use create_invoice for new invoices'), so the usage guidance is clear but not fully explicit about when not to use it.

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