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 nothing beyond that — no mention of behavior for an unknown/foreign Id, no note about company scoping ambiguity, no indication of the returned shape. With annotations carrying the burden, a 3 is appropriate.

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?

One sentence, front-loaded with the verb and resource, with the usage condition trailing. Nothing is padded, though the conditional clause is compact to the point of being cryptic.

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 read tool with full annotation coverage the description is adequate on inputs, but there is no output schema, so the agent has no idea what an employee record contains or what happens on a miss. One clause on the return payload or error behavior would close the gap.

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%: both 'id' and 'company' are fully described in the schema, including the optional-when-single-company rule. The description adds no format, casing, or resolution detail beyond what the schema already provides, so the 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?

The description states a specific verb and resource ('Get a single employee from QuickBooks Online by Id') and makes the single-record scope explicit, which separates it from list-oriented siblings. However, it never names the sibling it is contrasted with (search_employees) or acknowledges create_employee/update_employee by name, so differentiation requires the agent to infer from the generic phrase 'search or write'.

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?

It gives a conditional ('when no search or write answer already holds it'), implying an agent should exhaust search_employees first and use this only for a direct Id lookup — useful but phrased obliquely. No explicit when-not guidance, no named alternative, and 'write answer already holds it' is ambiguous (does a prior create response count?).

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