The Holder Performance Summary API provides insights into the performance of institutional investors based on their stock holdings. This data helps track how well institutional holders are performing, their portfolio changes, and how their performance compares to benchmarks like the S&P 500.
| Name | Required | Description | Default |
|---|---|---|---|
| cik | Yes | CIK number | |
| page | No | Page number (default: 0) |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must disclose behavioral traits. It does not mention that this is a read-only operation, return format, pagination behavior, or any required permissions. This leaves significant gaps for the agent to infer safety and side effects.
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?
Two sentences, reasonably concise, but the second sentence ('This data helps track...') is somewhat redundant with the first and adds fluff. Not every sentence earns its place, though it is not overly verbose.
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?
No output schema exists, so the description must convey what the response contains. It vaguely mentions performance, portfolio changes, and benchmarks but does not specify concrete output fields or structure. For a simple 2-parameter tool, the description is minimally adequate but leaves the agent guessing about the exact return.
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% and parameters are documented (CIK number, page number with default). The description adds no extra meaning beyond the schema, such as clarifying that the CIK refers to the institutional holder. Baseline 3 applies because schema covers all parameters.
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 states the tool provides insights into institutional investor performance based on holdings, but uses vague language like 'provides insights' rather than a specific action verb. It distinguishes somewhat from siblings by focusing on performance and benchmarks, but does not explicitly name alternatives.
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?
There is no guidance on when to use this tool versus alternatives like getHolderIndustryBreakdown or getFundHoldings. It mentions what the data helps track but does not provide context for choosing this tool.
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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