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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the description correctly avoids repeating those. It adds valuable context: data source (MFAPI), license (MIT), no authentication required, the existence of 20+ years of history, and the fact that returns are in INR with dates. This enriches the agent's understanding beyond the structured annotations without contradicting them.

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 well-structured and front-loaded with the primary action. It packs multiple relevant details (ordering, currency, history depth, limit behavior, lookup strategy, source/license/auth) into a compact set of sentences without excessive verbosity. Slight redundancy with the schema (limit defaults) is minor and does not detract from readability.

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?

The description covers all essential information an agent needs: what is returned (daily NAV, INR, dates), ordering, limit semantics, how to find the required scheme_code, data source and licensing, and clear use cases. The presence of an output schema removes the need to describe return structure. No significant gaps remain for correct invocation.

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%, so both parameters are already documented. The description adds practical semantics by explaining the limit parameter's default and max (redundant but reinforcing) and telling the agent where to obtain scheme_code (via mfapi.schemes.search). This helps disambiguate the required parameter beyond the raw 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 states a specific verb ('Get') and resource ('historical Net Asset Value (NAV) records for an India mutual fund scheme') with clear ordering ('most recent first'). It implicitly differentiates from the sibling mfapi.nav.latest by focusing on history, and explicitly routes to mfapi.schemes.search for scheme_code lookup. This gives an agent a precise understanding of what the tool does.

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?

The description provides clear usage context by listing intended analytical use cases ('performance analysis, CAGR calculations, SIP return modelling, trend visualization') and instructs the agent to use mfapi.schemes.search to find the required scheme_code. However, it does not explicitly contrast with the sibling mfapi.nav.latest for when to use history vs. current NAV, leaving that distinction implicit.

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