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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: it uses the investment-date NAV or the next available NAV date, defaults valuation to the latest NAV, and explicitly excludes stamp duty, exit load, and tax while noting it cannot project future returns.

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 dense sentences, front-loaded with the core calculation and scope, then the mechanic and the exclusions. No filler; every clause carries information.

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 read-only calculation tool with full schema coverage and no output schema, the description covers inputs semantics, the calculation method, the default valuation behavior, and the limitations (no tax/load/stamp duty, no future projection). Nothing an agent needs to invoke it correctly is missing.

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 already 3. The description adds calculation semantics the schema does not: units are bought at the NAV on the investment date (or the next NAV date if unavailable), and end_date defaults to the latest NAV, clarifying the optional parameter's behavior.

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 (calculate) and resource (lumpsum investment value in one Indian mutual fund scheme), and explains the mechanism (units at NAV on investment date, value at latest/chosen end date, gain, return, CAGR). Clearly distinguishable from siblings like calculate_sip_returns and compare_funds.

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?

Explicitly frames the use case as 'if I had invested X on date Y' questions, which anchors when to reach for it, and the scheme_code description points to search_mutual_funds as the source. It does not, however, explicitly say to use calculate_sip_returns for recurring investments, so the sibling routing is left partly implicit.

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