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 the meaningful precondition that the data is 'only meaningful with multicurrency enabled,' which is behavioral context not present in the annotations.

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?

Front-loads the verb and resource in the first clause and keeps everything to two sentences. The second sentence's opening phrase 'The currencies the company transacts in' borders on restating the resource, so it is efficient but not maximally tight.

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 no output schema and safety fully covered by annotations, the description supplies the key precondition (multicurrency) and the routing rule for search/write alternatives. It is complete enough to call correctly, though not exhaustive about failure modes when multicurrency is off.

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 both parameters (id, company) are fully documented in the schema. The description only echoes the by-Id lookup, adding no format, multi-company, or identifier semantics 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?

States a specific verb and resource (get a single company currency from QuickBooks Online) and pins the scope to a by-Id lookup. An agent can distinguish this from search_company_currencies or create/update/delete_company_currency without opening a 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 phrase 'when no search or write answer already holds it' routes the agent toward search/write siblings first, giving real when-to-use context. It stops short of naming search_company_currencies explicitly, so the guidance is implied rather than fully enumerated.

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