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

With no annotations provided, the description carries the full burden. It discloses significant behavioral details: money factor rent charge, residual-based depreciation, state tax methods, fee capitalization, zero-drive-off iteration, MSD money-factor discounts with ROI, and the auto-conversion between money factor and APR. This is rich context beyond the schema. It could mention the output format, but it does hint at buyout amounts. No contradiction with annotations (none).

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?

Three sentences, no waste. The first sentence is dense but every clause adds value (tax methods, fee cap, zero-drive-off, MSD). The second clarifies input selection, and the third gives use cases. It is front-loaded with 'Exact consumer car lease calculator' and maintains a logical flow.

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 complex 19-parameter tool, the description covers major behaviors: tax methods, MSD, zero-drive-off, and buyout computation. However, with no output schema, it doesn't state exactly what the return object contains (e.g., monthly payment, total cost). It also doesn't explicitly mention required parameters (msrp, term, residualPercent). These minor gaps prevent a 5.

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 already covers 89% of parameter descriptions, so the baseline is 3. The description adds critical value by clarifying the OR relationship between moneyFactor and apr ('Accepts either a money factor... or an APR (auto-converted)'), which the schema does not enforce. It also references zero-drive-off and MSD behaviors that map to parameters, enhancing understanding beyond raw schema definitions.

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 ('consumer car lease'), the action ('calculate'), and the exact scope ('real captive-lender math...'). It distinguishes itself from generic lease calculators by enumerating specific features like state tax methods, MSD discounts, and zero-drive-off iteration. This is a specific verb+resource with strong differentiation from siblings.

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 description ends with explicit use cases: 'verify dealer quotes, compare lease offers, or compute drive-off and lease-end buyout amounts.' This provides clear context for when to use the tool. However, it does not mention alternatives or exclusions (e.g., comparing to calculate_lease or solve_lease_structure), so it stops short of a 5.

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