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

Annotations already convey readOnlyHint=true, and the description aligns with that by presenting this as a lookup/selection tool. It adds useful context about the returned data (categories, paid-from accounts, codes) and the company-specific scope, which is valuable given there is no output schema.

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 sentence that front-loads the core identity ('The expense accounts you can post to in this company') and then elaborates with the precise selection information. Everything present earns its place, with no filler or redundancy.

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 zero-parameter, no-output-schema tool, this description is complete. It states what the tool returns (company postable expense accounts), what fields are available (category, paid-from, code), and the intended workflow (shaping a paid-expense draft).

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 has zero parameters, so the baseline is 4. The description's mention of picking a category and paid-from account by code refers to the output content rather than input parameters, which is consistent with the empty schema.

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 clearly identifies the resource: a list of expense accounts available for posting in this company. It specifies what can be picked (category and paid-from account) and by what identifier (code), distinguishing it from sibling tools like create_expense_draft or expenses_summary.

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 provides a clear usage context: 'for shaping a paid-expense draft' tells an agent when to use this tool. However, it does not explicitly name alternatives or exclusion conditions, so it does not fully route the agent away from similar expense-related tools.

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