krx-etf-mcp

compare_etf

Compare ETF price returns across multiple funds for any period. Set custom dates or use a months lookback to analyze relative performance.

Instructions

Compare price returns of specific ETFs over one shared period.

Args: codes: 6-digit short codes to compare. months: Lookback when start_date is omitted. start_date: YYYYMMDD override for the period start. end_date: YYYYMMDD override for the period end.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "codes": "<codes>"
    },
    "name": "compare_etf"
  }
}

Input Schema

Name	Required	Description	Default
`codes`	Yes
`months`	No
`end_date`	No
`start_date`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Aug 13, 2026

TDQS

A4.1/5.0

Behavior3/5

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

No annotations are present, so the description bears the burden. It does disclose behavioral details: 'months: Lookback when start_date is omitted' and 'start_date/end_date override' clarify precedence and parameter semantics. However, it omits output format, error handling, and edge cases (e.g., invalid codes, mismatched periods), leaving some behavioral gaps.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description leads with a one-sentence purpose, followed by a tight Args list. Every line earns its place; there is no redundancy or filler. The structure is scannable and appropriately sized for the tool's complexity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

All four parameters are semantically explained, and an output schema exists, so return values don't need description. It lacks explicit usage alternatives and edge-case handling, but the provided information is sufficient for correct basic invocation. A perfect score would require more guidance on when to prefer alternatives like get_etf_history or rank_etf_return.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema has 0% description coverage, but the Args section fully compensates. It explains that codes are 6-digit, months is a lookback when start_date is omitted, and start/end dates are YYYYMMDD overrides with explicit precedence. This adds significant semantic meaning beyond the schema's bare types and defaults.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool 'Compare price returns of specific ETFs over one shared period,' identifying both the action (compare) and the resource (price returns of ETFs). This differentiates it from siblings like get_etf_history (single ETF history) and rank_etf_return (ranking), making its purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage context is implied through phrases like 'over one shared period' and the argument descriptions (months as lookback, start/end overrides), but no explicit 'use when' guidance or exclusions are provided. The description doesn't contrast with sibling tools, so an agent must infer when this is the preferred choice.

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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