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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds that no organisationId scoping is required, which is genuine context, but says nothing about result count behavior, ordering, or what happens when multiple invoices match.

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, front-loaded with the action and resource, with zero filler. The phrase 'No organisationId needed' is terse to the point of being cryptic about why that matters, which costs a point.

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 simple read-only lookup with a fully documented four-parameter schema and annotations covering the safety profile, the description is nearly sufficient. The one real omission is its relationship to the InvoiceInvestigation sibling, which affects tool selection.

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 description coverage is 100%, and the schema documents limit, intentId, and unpaidOnly. The description adds only the meaning of query (invoice number or email), which the schema already states. Baseline 3 applies since the schema does the heavy lifting.

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 (find customer invoices) and names the two accepted lookup keys (invoice number or customer email). It does not distinguish itself from the sibling InvoiceInvestigation, so an agent cannot tell from the description which of the two to reach for.

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?

Usage is implied by the lookup keys and by the note that no organisationId is required, which suggests a quick standalone lookup. There is no explicit when-to-use versus InvoiceInvestigation, and no exclusions or alternatives named.

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