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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description adds genuinely useful context beyond them: it discloses that returns are computed from NAVs only and exclude exit load and tax, which materially affects how the agent should present the numbers. It does not mention pagination or error behavior, keeping it out of the top band.

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 action, and every clause earns its place by either scoping the lookup or enumerating the payload. The long enumeration in sentence one is dense but functional, not padding.

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?

There is no output schema, so the description usefully enumerates the return fields (NAV, returns, CAGR, 52-week range, plan/option). Combined with the tax/exit-load caveat, an agent has enough to call and interpret the tool, though it omits any note on data staleness or failure modes.

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?

With one parameter at 100% schema coverage, the schema already documents the 6-digit AMFI scheme code and points to search_mutual_funds as its source. The description's mention of 'AMFI scheme code' repeats rather than extends that, so the 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 specific verb and resource ('Get the latest official NAV and NAV date for one Indian mutual fund scheme by AMFI scheme code') and enumerates the returned metrics, so the agent knows exactly what this does. It is clearly a NAV/returns lookup rather than a calculator, but it never names the sibling tools (calculate_lumpsum_returns, compare_funds) to sharpen the distinction, so it falls short of the top band.

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?

'Use when the user asks for a fund's NAV today or its returns' gives a concrete trigger condition. There is no when-not guidance and no explicit routing to the calculate_* or compare_funds siblings, which would be the natural alternatives for return computations.

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