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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description's claim about returning payers, splits, and change history is largely duplicated by the output schema, so it adds little behavioral context beyond what structured fields provide.

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 short fragment that is front-loaded with the core noun. It wastes no words, though the sentence fragment lacks a verb to anchor the action.

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 one-parameter read tool with an output schema and read-only annotations, the essential safety and return-shape information is available elsewhere. The missing piece is routing guidance versus sibling read tools, which leaves the definition adequate but with clear gaps.

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 0% and the single parameter (expense_id) is never mentioned in the description. The description does nothing to compensate for the missing parameter documentation, even though the parameter is relatively self-explanatory by name.

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 the resource ('One expense') and enumerates what it carries (payers, splits, change history), which implicitly distinguishes it from the collection sibling list_expenses. No explicit verb, but the singular scope makes retrieval unambiguous.

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?

No when-to-use guidance, no prerequisites, and no mention of alternatives such as list_expenses or get_activity. The only inference available is that it needs an expense_id, which comes from the schema, not the description.

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