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

Annotations already cover safety (readOnly, idempotent, non-destructive), and the description adds substantive computation context: three times the RBI Bank Rate (17.25%), monthly compounding, and the accrual start (day after the payment deadline). It does not state the output shape or rounding/format behavior beyond 'exact to the paisa'.

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?

A single well-packed sentence: purpose first, then the formula, rate, compounding, and accrual window, closing with precision. Every clause carries information an agent or user needs, with no repetition of schema fields.

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 deterministic read-only calculator with no output schema, the description covers the computation method and precision well enough to call it correctly. The only residual gap is the return value's exact shape (numeric amount vs. formatted currency), which 'exact to the paisa' only hints at.

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 description coverage is 100%, so the schema already documents all four parameters, including the 45-day cap and the paid_on default. The description adds only the accrual start logic tied to invoice date, which is marginal over what the schema provides; baseline 3 is appropriate.

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 precise verb+resource (calculate MSMED late-payment interest) and pins the domain with the exact legal basis, Section 16 of the MSMED Act, and the payer/payee roles. An agent can distinguish it from calculate_gst or calculate_upi_mdr without opening any schema.

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?

Implies the triggering situation clearly: a buyer paying a Udyam-registered micro/small supplier late, past the agreed credit period (max 45 days). It does not name an alternative tool or state explicit exclusions, but the domain conditions are specific enough that an agent knows when it applies.

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