Analyst and Risk Officer: 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 cover safety (readOnly, idempotent, non-destructive, closed-world), so the description's real contribution is the fail-closed policy: it refuses rather than estimating when data is missing, and the value is tied to what ETFIQ published. That is meaningful behavior beyond annotations, though the shape of a refusal (error vs. explanatory text) is left unstated.
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 that front-load the core metric, then usage, then failure mode – no filler. The leading "Analyst and Risk Officer:" audience tag is slightly distracting but does convey intended consumers.
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?
There is no output schema, so the description carries the return-value burden, and it only gestures at "how much of their weight" without stating form (percentage), granularity, or what accompanies it. Combined with undocumented parameters, an agent can guess the intent but not the exact calling convention.
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 0% and both parameters are opaque single letters, a and b, with no descriptions or enums. The description only implies they are the two funds in the pair; it never says whether they take tickers, fund names, or page slugs, nor whether order matters for the result.
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?
States a concrete verb+resource: the shared weight two funds hold in common, sourced from the ETFIQ comparison page for that pair. It is clearly narrower than generic siblings such as etf_compare or etf_holdings, though it never names a sibling explicitly to sharpen that boundary.
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?
Gives an explicit use case ("whether two ETFs are the same thing, or whether owning both adds anything") and explicit failure conditions (pair not compared, or either holdings book incomplete). What it lacks is a named alternative for those cases – the agent must infer that etf_compare or etf_holdings is the fallback.
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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