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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is known; the description adds the genuinely non-obvious part — the blast radius is limited to future generation and already-issued invoices are untouched. What's missing is permission requirements and whether the deletion is reversible.

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, each earning its place: effect, scope of destruction, and the confirm requirement are front-loaded in that order. No filler or restatement 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?

For a two-parameter destructive tool with full schema coverage, annotations, and no output schema, the description supplies everything an agent needs: what is deleted, what survives, and how to preview safely.

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% and the confirm parameter's description in the schema is actually richer than the tool description (it explains that any value other than boolean true yields a preview). The description restates the confirm semantics but adds nothing about recurringId beyond what the schema says.

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 ('Deletes a recurring invoice') and immediately bounds the effect: 'no more invoices are made from it' while 'the invoices it already made stay as they are.' That scope clarification separates it cleanly from void_invoice, delete_invoice_draft, and update_recurring_invoice without the agent needing to open 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?

Gives explicit operational guidance for the confirm flag: 'Needs confirm: true; without it the result is a preview,' which tells the agent exactly how to run a safe dry-run first. It does not, however, address when to delete versus archive/update a recurring invoice, nor mention prerequisites.

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