How much of their weight two funds hold in common, as ETFIQ published it on the comparison page for that pair. Use when asked whether two ETFs are the same thing, or whether owning both adds anything. Refuses rather than estimating when the pair is not compared or either holdings book is incomplete.
| Name | Required | Description | Default |
|---|---|---|---|
| a | Yes | ||
| b | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already mark it read-only, idempotent, and non-destructive. The description adds the data source, the refusal behavior ('Refuses rather than estimating'), and the specific incomplete-book condition, giving the agent genuinely useful behavioral context beyond the annotations.
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?
Three short sentences: core semantics first, use case second, refusal boundary third. There is no filler or duplication of annotation content.
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?
For a simple two-parameter read-only tool, the description covers source, use case, and failure mode. Since there is no output schema, it leaves the exact return representation/units implicit, and identifier formatting is unstated, but the core semantics are inferable.
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?
With 0% schema coverage, the description must explain 'a' and 'b.' It conveys that they are the two funds being compared and that the result is common weight, but it never states the identifier format (e.g., tickers or ETFIQ codes) or otherwise documents the string values. This is partial compensation.
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 clearly defines the tool as computing the shared weight between two funds as published by ETFIQ on the comparison page. It names the resource (fund pair) and the metric (overlapping weight), and the concept is distinct from the holdings-focused sibling tools.
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?
It explicitly states the target questions: 'whether two ETFs are the same thing, or whether owning both adds anything.' It also clarifies when it will refuse. It does not name alternatives or an explicit when-not-to-use condition, so it falls just short of a 5.
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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