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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds useful provenance ('from the payments' splits') and an output distinction ('saying which were split by the schedule rather than the lender'), though it does not explain default behavior when year is omitted.

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 description is a single dense sentence with no filler, but it is a sentence fragment lacking a clear main verb. The final clause is somewhat awkward, though it is concise overall.

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 simple read-only report with one optional parameter and no output schema, the description gives the key output categories and data source. However, it omits what happens when 'year' is omitted and does not describe the return structure, leaving meaningful 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?

The schema fully documents the single optional 'year' parameter with an example. The description reinforces the yearly scope but adds no format or default-behavior details beyond what the schema provides, so 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?

The description clearly identifies the resource and scope: interest, principal, and escrow paid per loan in a year, derived from payment splits. It does not explicitly distinguish itself from siblings like loan_get or loan_loans, but the reporting nature is evident from the content.

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?

Usage is implied by the phrase 'per loan in a year' and the reporting focus, but there is no explicit guidance on when to choose this tool over siblings. No alternatives or exclusions are named.

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