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

Annotations already cover safety (readOnly, idempotent, closed-world), so the description's job is to add context — and it does: it discloses the equity tax treatment assumption (capital gains plus 4% cess, surcharge excluded), multi-currency support, and that step-up compounds annually. It does not state whether a year-by-year schedule is returned or how the response is structured.

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?

Two tight sentences plus a URL, with the concrete example front-loaded so an agent immediately sees scope and magnitude. Nothing is redundant with the schema.

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 no output schema, the description should clarify what comes back (corpus, invested amount, gain, tax, schedule breakdown). It gives only a single illustrative figure, leaving the return shape ambiguous for an agent that must present results.

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% and includes units, ranges, defaults and even enum semantics, so the baseline is 3. The example ties the default amount/years/rate to a result, which adds intuition, but it doesn't explain the interplay of stepUp or fundTax beyond what the schema already says.

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 names the resource (SIP calculator) and a distinguishing feature (annual step-up, tax on redemption for residents and NRIs), and the worked example makes the computation concrete. It never explicitly contrasts with near-neighbours like compound_interest_calculator or future_value_calculator, but an agent can infer the monthly-instalment framing.

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?

Usage is only implied: '10,000 a month' signals periodic contributions rather than a lump sum, and the step-up mention hints at salary-increment scenarios. There is no explicit when-to-use or when-to-prefer-an-alternative statement, and no guidance on NRI-specific inputs despite the mention.

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