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

The destructiveHint annotation already signals a mutating write, so the bar is lower, but the description adds nothing behavioral beyond it: no auth/permission requirements, no statement about what side effects occur (e.g., whether the re-invoice flag triggers downstream billing), and no return information. The 'optionally tied to...' clause restates parameters rather than disclosing behavior.

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?

Two tight sentences with the core purpose front-loaded and the endpoint noted compactly. Nothing is wasted, though the endpoint string is marginally redundant given the tool name.

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 14-parameter mutation with no output schema and minimal annotations, the description covers the core intent but leaves gaps: it does not explain success/return behavior or how the optional relations interact. It is minimally adequate rather than complete.

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 79%, near the high band, so the schema documents most parameters (client_id, vendor_id, project_id, should_be_invoiced, etc.) itself. The description merely echoes a few of these relationships and adds no syntax, format, or default information beyond the schema, so the baseline of 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 ('Log an expense') and names the optional relations (vendor, client, project) plus the re-invoice flag, so the agent knows exactly what operation this is. It is distinguishable from sibling creators like create_invoice or create_client by resource, though it never explicitly contrasts them.

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?

There is no when-to-use guidance, no prerequisites, and no mention of the obvious alternative (list_expenses) or any exclusion. Usage is only implied by the verb 'Log'.

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