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

Annotations already declare readOnlyHint=false and destructiveHint=false; the description adds real context beyond them by explicitly stating the invoice and existing notes are unchanged, and by naming the underlying call (SOAP InsertInvoiceNote). It stops short of addressing duplicate behavior, which matters given idempotentHint=false — calling twice presumably yields two notes, and that is not said.

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?

Two short sentences, no filler, and the most decision-relevant token ('WRITE') is front-loaded. Every clause carries information: mutation type, target, ID provenance, and non-destructive scope.

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 three-parameter write tool with annotations and no output schema, the description covers purpose, safety profile, ID provenance, and the underlying API. The remaining omission — no statement about what (if anything) is returned, such as a note ID, and no warning about duplicate notes on retry — is minor but real.

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 baseline is 3, but the description adds value by telling the agent that invoice_id is the numeric InvoiceDBID found in invoice replies — a provenance hint the schema does not give. The optional note_date parameter is not mentioned in the description, leaving that gap to the schema.

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 (add a note to a sales invoice) and pins the target key (InvoiceDBID), which cleanly separates it from the read-side sibling kashflow_get_invoice_notes. An agent can identify the operation 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?

The 'WRITE:' prefix and 'Existing notes and the invoice are not changed' establish the conditions under which this is appropriate (an additive annotation on an existing invoice), and the parenthetical explains where the required ID comes from in invoice replies. It does not name or exclude the read counterpart kashflow_get_invoice_notes, so routing guidance is clear but incomplete.

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