get_fund_nav

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

With no annotations provided, the description carries the full burden. It discloses that the data comes 'from live MFAPI.in data' and, more importantly, that 'a wrong code silently returns a completely different fund.' This goes beyond the basic action and warns of a critical failure mode, which is valuable transparency.

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 sentences pack a clear purpose and a critical usage warning. Every clause adds value, and the description is appropriately sized for the tool's simplicity.

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 tool without an output schema, the description covers the essential operational context: the live data source, the need to use search_mutual_funds for the code, and the danger of incorrect codes. It doesn't describe the return format, but that is less critical for a NAV getter.

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 covers the parameter well (description and example), so baseline is 3. However, the tool description adds crucial semantics: the schemeCode must come from search_mutual_funds and must never be guessed or reused, with the consequence of silent wrong results. This adds meaning beyond the schema.

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 clearly states the tool's function: 'Get the latest Net Asset Value (NAV) for a mutual fund scheme from live MFAPI.in data.' It uses a specific verb and resource, and the explicit link to search_mutual_funds distinguishes it from sibling tools like get_benchmark_rates or calculate_fund_returns.

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 provides strong usage guidance by stating the schemeCode 'MUST be obtained from search_mutual_funds output' and warning 'NEVER guess a code or reuse one from memory.' This clearly instructs the agent on the required prerequisite and the correct alternative tool to use, though it doesn't explicitly mention competing tools for the same task.

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