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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false): discloses the draft status and absent invoice number, the returned net/VAT/total, that the draft is inert and deletable, that no confirmation is needed, and the API-key requirement. This is exactly the side-effect and auth context annotations cannot convey.

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-loads purpose, then adds scoping, workaround, and safety context in tight sentences. The 'Bokio: Create a draft invoice...' lead mildly duplicates the title, but every subsequent sentence earns its place.

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 still tells the agent what comes back (net, VAT, total), covers the write/draft side effects, the discount limitation, and auth needs. Nothing material for correct invocation 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 coverage is 100%, so the baseline is 3, but the description adds meaning by explaining the per-line discount limitation ('add a line with a negative unit price instead'), which directly informs how to populate unit_price and lines. That is genuine value beyond the schema text.

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 ('create a draft invoice for a customer with its lines') and immediately distinguishes the outcome from siblings by noting 'publishing is a separate tool'. An agent can tell this apart from bokio_publish_invoice/bokio_send_invoice without opening any 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?

Explicitly frames when to use it ('runs without asking first' because a draft reaches no one) and names the alternative ('publishing is a separate tool'), plus a workaround for the discount case. It gives clear context but does not exhaustively enumerate when-not-to-use versus all draft/invoice siblings.

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