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

Annotations already supply readOnly/idempotent/non-destructive, so the bar is lower, yet the description still adds real behavioral context: all metrics are computed to the same as-of date, and it flags mixed categories, Direct vs Regular plans and IDCW options. It doesn't cover error handling for invalid codes, but the added traits are substantive.

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?

Three tight sentences, front-loaded with the action, scope and input, then the returned metrics, then when-to-use and the negative scope. No filler or repetition of the title.

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?

With no output schema, the description compensates by enumerating the returned metrics (NAV, category, plan, option, 1M/3M/6M/1Y returns, 3Y/5Y/10Y CAGR) and the same as-of date guarantee. Combined with 100% schema coverage, an agent has everything needed to call it correctly.

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% and there is only one parameter, so the schema does the heavy lifting (minItems/maxItems, 6-digit code format). The description's '2 to 5' and 'by AMFI scheme code' restate schema constraints rather than adding new syntax or format meaning.

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 (Compare) plus resource (mutual fund schemes), the exact input identifier (AMFI scheme code), the cardinality (2 to 5), and precisely which fields are returned. It is immediately distinguishable from get_fund_nav (single NAV) and search_mutual_funds (discovery).

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 wants to compare funds' past performance' gives a clear triggering condition, and 'It does not rank or recommend funds' sets a useful exclusion. It stops short of naming the sibling tools (e.g., use get_fund_nav for a single fund), so routing is inferred rather than explicit.

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