xoomar-mcp

13F institutional holders of a stock

fund_holders

Find which tracked 13F managers held a US ticker in their latest quarterly filing, including shares, value, portfolio share, and change.

Instructions

Which tracked 13F managers (Berkshire, Bridgewater, Citadel, Renaissance and others) held a ticker at their latest quarterly filing: shares, value, share of portfolio, change.

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": {
      "ticker": "<ticker>"
    },
    "name": "fund_holders"
  }
}

Input Schema

Name	Required	Description	Default
`ticker`	Yes	US ticker symbol, e.g. GME. Class shares as on the SEC list, e.g. BRK-B.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.1Sep 13, 2026

TDQS

B3.2/5.0

Behavior3/5

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

With no annotations, the description carries the full burden. It does disclose two meaningful behavioral traits: the universe is limited to 'tracked' 13F managers, and data reflects the 'latest quarterly filing', implying lag and quarterly cadence. It says nothing about read-only safety, empty results for untracked tickers, or error behavior.

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?

A single sentence that front-loads the core question and then appends the returned attributes compactly. Dense but no wasted clauses; the parenthetical manager examples add credibility without bloat.

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?

No output schema exists, so the description must convey the return shape, and it does (shares, value, share of portfolio, change). For a single-ticker lookup it is nearly complete; it omits how many managers are returned and what happens for untracked tickers.

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?

Only one parameter exists and the schema documents it at 100% coverage (US ticker, class-share format like BRK-B). The description adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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

Purpose4/5

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

States a specific resource (13F institutional holders) and the exact question answered ('which tracked managers held a ticker at their latest quarterly filing'), and even names the return fields. It does not explicitly distinguish itself from the closely related siblings large_holders and fund_portfolio (the inverse lookup), so it falls short of a 5.

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

Usage Guidelines2/5

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

The usage is only implied — an agent can infer this answers 'who owns this stock' — but there is no explicit when-to-use, no exclusions, and no routing to alternatives such as large_holders or fund_portfolio, which are the obvious competing choices for holder data.

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