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

Annotations already declare readOnlyHint/idempotent/non-destructive, so the bar is lower, and the description adds real context: the fee terms source (a 2025 PSA), rates and minimums, and what gets returned. It could still say whether inputs are validated or how the outcome enum gates optional parameters, but the disclosure is strong.

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 purpose and the fee terms, then closes with the return shape. It is dense but every clause earns its place; slight density in the fee-rate enumeration keeps it from a 5.

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?

With 6 parameters and conditional-required fields all documented in the schema, and no output schema, the description supplies the return-value summary and the fee model needed to interpret results. An agent has enough to call it correctly; minor gap is that it doesn't restate which optional inputs pair with which outcome.

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% and each parameter already has a descriptive note including conditional requirements (proceeds for payoff, note_rate/months_to_maturity for corrected). The description adds no parameter-level detail beyond the outcome naming, 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?

States a specific verb (estimate) and resource (special servicing/workout/liquidation fees) and enumerates the three outcome branches the tool models. Clearly differentiable from siblings like special_servicing_timeline, which covers timing rather than fee math.

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?

The three-outcome framing (corrected, refi120, payoff) implicitly tells the agent when each computation applies, and the description makes clear this is a fee-estimation tool for a single outcome. It does not explicitly name a sibling or state exclusions, so it falls short of a full 5.

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