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

Beyond the annotations (readOnlyHint=false, idempotentHint=false, destructiveHint=false), the description discloses the effects: the split is recorded, the row posts once through the loan, and surplus above the scheduled payment plus escrow is allocated to principal. It does not say what happens on a repeated link or on a failing split, which matters given idempotentHint=false.

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?

Front-loaded with the core action and outcome, then the split rules, then effects. Slightly dense and the second paragraph packs several rules into long sentences, but nothing is redundant with the schema or annotations.

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?

There is no output schema, and the description covers the resulting state (payment split and recorded, row posts once) and notes that the result indicates when the schedule computed the split. For a non-idempotent financial mutation it could still spell out re-link/duplicate behavior and failure modes when the split doesn't add up.

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 100%, so the schema already explains each field's type and units. The description still adds real semantics: the split fields must sum to the row amount, they are optional and only used when the lender printed them, and unmapped excess flows to principal.

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 verb+resource: ties a statement row to a loan and records the split into principal, interest and escrow. It is clearly distinguishable from siblings loan_candidates (discovery) and loan_unlink_payment (reverse operation) by naming the row-linking action and its outcome.

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?

Explicitly routes the agent to loan_candidates to find candidate rows, and gives a clear rule for the two modes: pass the lender's printed split when available, otherwise let the schedule derive it. It stops short of naming loan_unlink_payment as the reverse or stating when not to use this tool, so it is clear context rather than full when/when-not guidance.

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