Full calendar-year (Jan-Dec) total return for one fund. Pass year, or omit for the latest completed year. calendar_year_return is a decimal fraction, distributions reinvested (0.263 = +26.3%); base_date/end_date give the actual span (partial in launch/delist years). Use getTrailingReturns for rolling windows.
| Name | Required | Description | Default |
|---|---|---|---|
| pathParams | Yes | ||
| queryParams | Yes |
Changes observed during successful MCP inspections.
Input schema / properties / pathParams / properties / code / descriptionAdded value: +"The fund's bare ticker, case-sensitive — e.g. `SPY`, `QQQ`, `VTSAX`. If you only have a name, resolve it with searchFunds first."Input schema / properties / queryParams / properties / year / descriptionPrevious value: -"Specific calendar year. Omit for latest."New value: +"A four-digit calendar year, e.g. `2022`. Omit for the fund's most recent completed year."Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description explains the meaning of the return fields (decimal fraction, distributions reinvested) and the actual span of base_date/end_date, including partial years for launch/delist cases. This gives a transparent picture of the tool's behavior without requiring external assumptions.
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 concise, comprising three sentences that pack essential information: function, parameter usage, return semantics, and differentiation from a sibling tool. No redundant or vague wording is present.
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 is self-contained: it explains the tool's purpose, parameter behavior, return value interpretation, and points to the correct alternative for different use cases. It covers all necessary context for a user to decide when and how to invoke the tool.
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?
Both parameters are thoroughly described in the schema and further clarified in the description: year's optionality and format, and market's informational role. The description adds context beyond the schema by explaining the meaning of the return values, enhancing parameter understanding.
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: retrieving full calendar-year total returns for a single fund. It distinguishes this from getTrailingReturns, which covers rolling windows, eliminating ambiguity.
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?
Explicit instructions are given: pass a specific year or omit it to get the latest completed year. The description also notes that market is informational and defaults to US, and directs users to getTrailingReturns for rolling windows, providing clear when-to-use guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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