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

The annotations already declare the tool read-only, idempotent, and non-destructive. The description adds meaningful context beyond that: publication frequency ('published by AMFI daily on business days'), the fact that the returned date reflects the last published value, the data source and license (MFAPI, MIT), and the absence of authentication requirements. This tells an agent exactly what side effects and freshness to expect.

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?

The description is four sentences, front-loaded with the tool's core purposeches. Every sentence adds a distinct, useful fact: input, output, publication cadence, sibling guidance, and data provenance. There is no repetition or excess verbiage.

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 single-parameter lookup tool with an output schema, the description covers everything needed for correct invocation: the required input, how to obtain it, what output to expect (with a pointer to the output schema for structure), data freshness, source, license, and auth. No meaningful gap remains.

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 documents scheme_code thoroughly (type integer, description that it is an AMFI code and how to get it), and the schema description coverage is 100%. The tool description repeats 'by its AMFI scheme code' but adds little beyond what the schema field already states. It meets the baseline for high schema coverage, but does not elevate it further.

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 opens with a precise verb-resource pair: 'Get the most recent Net Asset Value (NAV) for an India mutual fund scheme by its AMFI scheme code.' It lists the exact output fields (NAV in INR, date, fund house, scheme type, category, ISIN) and explicitly names the sibling for finding the scheme code, so there is no ambiguity about what this tool does or how it differs from mfapi.schemes.search.

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?

It explicitly directs the user to mfapi.schemes.search for finding the required scheme_code, which is valuable. It also implies the latest-vs-history distinction by saying 'most recent' and 'last published value,' though it never mentions mfapi.nav.history as the alternative for historical NAVs. That omission prevents a 5 because the when-not-to-use case is only implied, not stated.

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