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

Annotations only declare readOnlyHint and openWorldHint; the description goes far beyond that, explaining that expenseCategories is a CURATED subset, listing exactly what is excluded (cash/bank, A/R and Inventory controls, contra accounts, engine-only accounts), and detailing the distinct validation rule for category vs. paid-from codes. This is rich operational context an agent needs to avoid picking a rejected code.

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?

The content is substantive, but it is delivered as one dense run-on paragraph with nested asides that make the core point hard to extract. It front-loads the resource name but buries the practical routing guidance mid-sentence, hurting scannability.

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 no parameters, the description carries the semantic burden and mostly does: it explains what the list contains, what it excludes, and the filing-time validation for each code type. It stops short of describing the return shape (e.g. code-plus-name entries) or ordering, which would fully 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?

The tool takes zero parameters, so there is no parameter semantics to document; baseline for a param-less schema is 4. The description instead explains the meaning of the values the tool returns, which is a reasonable substitute.

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 resource — the expense accounts postable in this company, split into category and paid-from codes. It even ties the purpose to a workflow ("for shaping a paid-expense draft"), which is clearer than a bare name restatement. It does not explicitly distinguish itself from sibling lookups like search_expenses or find_in_taokeh, so it falls short of a 5.

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?

Gives clear context: use it to pick a category and paid-from code when building a paid-expense draft, plus the acceptance rule at filing time for each code type. It effectively tells the agent what codes are valid where, but never names a sibling alternative or states when NOT to call it.

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