fund_holdersWhich tracked 13F managers (Berkshire, Bridgewater, Citadel, Renaissance and others) held a ticker at their latest quarterly filing: shares, value, share of portfolio, change.
| Name | Required | Description | Default |
|---|---|---|---|
| ticker | Yes | US ticker symbol, e.g. GME. Class shares as on the SEC list, e.g. BRK-B. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are present, so the description carries the full burden. It does add useful context: 'tracked' signals a curated manager list, and 'latest quarterly filing' discloses the data's point-in-time recency. However, it omits error behavior, what happens for unknown tickers, and the full response shape.
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?
A single front-loaded sentence that packs purpose and output fields with zero waste. Every word earns its place.
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?
Adequate for a simple single-parameter query tool that discloses its output fields. The main gap is the missing usage guidance versus siblings; without it the agent may struggle to route correctly between manager-level and holder-level tools.
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 coverage is 100%: the ticker parameter already carries a clear description with examples (GME, BRK-B) and SEC class-share nuance. The tool description adds nothing beyond that, so the baseline 3 applies.
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 uses a specific verb-resource pairing ('which tracked 13F managers held a ticker') and enumerates the returned fields (shares, value, share of portfolio, change). It names concrete managers (Berkshire, Bridgewater) which helps set it apart from large_holders and fund_portfolio, though it stops short of explicitly naming those siblings.
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?
No guidance on when to select this tool over the closely related siblings fund_portfolio or large_holders. The agent must infer that this is the manager-level view of a ticker, with no stated exclusions or alternative routing.
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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