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 still adds value beyond the schema by disclosing the shape of the returned data (header, line items, label count for the period, related surcharges), which matters since there is no output schema; it stops short of mentioning error behavior for unknown invoice numbers.

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?

A single front-loaded sentence identifying the resource, the key, and the returned content with zero filler. Every clause carries information the agent can use.

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 only two parameters and no output schema, the description covers the essential need by listing what the investigation returns. Minor gaps remain: no statement of what happens when the invoice is not found, no pagination or size expectations, and no explicit routing from FindInvoice.

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%, so both parameters (invoiceNumber, intentId) are already documented in the schema. The description only echoes that lookup is by invoice number, adding no syntax, format, or correlation-ID guidance beyond what the schema provides, so baseline 3 applies.

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 ('invoice deep-dive') and resource ('by invoice number') and enumerates what the result contains: header, line items, label count in period, related surcharges. It is clear what the tool does, but it does not differentiate itself from sibling 'FindInvoice', so an agent must infer that 'deep-dive' means full detail rather than a lookup.

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 phrase 'deep-dive' implies this is the detailed follow-up to a search, and the sibling names FindInvoice and OrderInvestigation make that contrast inferable, but the description never states when to use this versus those alternatives or what prerequisites exist (e.g. whether the invoice number must come from FindInvoice).

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