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narumiruna

Yahoo Finance MCP Server

yfinance_get_holders

Read-onlyIdempotent

Retrieve major, institutional, and mutual fund holders plus insider transactions for any stock ticker to analyze ownership and insider activity.

Instructions

Fetch major holders, institutional holders, mutual fund holders, and insider data.

Returns JSON with:
- major_holders: Aggregated breakdown including insider % held, institutional % held,
  institutional % float held, and institution count.
- institutional_holders: List of institutional investors with shares held, date reported,
  value, and % change.
- mutualfund_holders: List of mutual fund holders with same fields.
- insider_transactions: Recent insider transactions including shares, value, transaction
  type, and date.
- insider_purchases: Summary of insider buy/sell activity over the last 6 months.
- insider_roster: List of known insiders by name and position.

Use this to analyze ownership concentration, insider activity, and institutional interest.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
symbolYesStock ticker symbol (e.g., 'AAPL', 'GOOGL', 'MSFT')
max_rowsNoMaximum rows returned per holder section. Use 0 to return all rows.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

Annotations already indicate readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true. The description adds value by detailing the JSON structure returned, including sections like major_holders and insider_transactions, which goes beyond the annotations and output schema.

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

Conciseness4/5

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

The description is concise, with a clear first sentence stating the purpose, followed by a bulleted list of return sections. It is well-structured and front-loaded, though the bullet list could be slightly more compact without losing clarity.

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?

Given the presence of an output schema and comprehensive annotations, the description provides sufficient context about the data returned. It lists the sections but does not cover edge cases like empty results or rate limits. However, for a read-only tool with openWorldHint, this is adequate.

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

Parameters3/5

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

Schema description coverage is 100%, so baseline is 3. The description does not add additional meaning to the parameters beyond what is in the schema (symbol and max_rows). The schema already provides descriptions for both parameters.

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 fetches major holders, institutional holders, mutual fund holders, and insider data. It distinguishes from siblings like yfinance_get_financials which deal with financial statements, making the purpose specific and unambiguous.

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

Usage Guidelines4/5

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

The description explicitly states 'Use this to analyze ownership concentration, insider activity, and institutional interest,' providing clear context for when to use. It does not explicitly mention when not to use or list alternatives, but the sibling tools cover different data types, making the usage fairly clear.

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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