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

With no annotations, the description carries the burden and does well: it explains the internal fitting procedure, that results are ranked by RMS error, and crucially that inferred day-count and capitalisation conventions are estimates rather than confirmed bank terms. It omits runtime/cost expectations for a grid search over up to 2000 rows, which keeps it out of 5 territory.

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 mechanism, then prerequisites, then the accuracy caveat — a sensible ordering. The opening sentence is long and clause-heavy, but every clause describes a distinct part of the computation rather than padding.

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?

An output schema exists, so return shape need not be described. The description covers inputs, fitting methodology, and interpretive limits, which is enough for a nested-schema, four-parameter analytical tool. A note on how confidence degrades with few checkpoints would have completed it.

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 baseline is 3; the description still adds real meaning by stating that the rows must be chronological with at least one ratePct and that balance checkpoints are what the fit uses. Those constraints are not obvious from the schema alone, so it edges above baseline.

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 concrete verb and resource ("forensic audit of a mortgage statement") and then specifies the mechanism: day-by-day replay, grid search over day-count/capitalisation/rounding conventions, RMS ranking, and overcharge reporting. This is clearly distinguishable from the sibling parse_mortgage_statement_text, which only extracts data, and from simulate_mortgage, which projects rather than audits.

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?

"Use to audit an actual mortgage statement" plus explicit preconditions (statement rows, at least one usable rate, sufficient balance checkpoints) tells the agent when the tool applies and what makes an input valid. It stops short of naming the alternative parse tool or saying when not to use it, so it earns a 4 rather than a 5.

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