The benchmark ETFIQ measures one ETF against, as its page names it: the index the fund names, or its own holdings, never a category stand-in; how that was set, the ETF it is priced through, and the fund's return, the benchmark's and the gap for each window. The ETFIQ benchmarks for model portfolios are a different thing (list_benchmarks).
| Name | Required | Description | Default |
|---|---|---|---|
| ticker | Yes | One fund's ticker, such as JEPI. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly/idempotent/non-destructive, so the description's job is to say what comes back — and it does: how the benchmark was set, the ETF it is priced through, and fund/benchmark returns plus the gap per window. With no output schema, this disclosure is genuinely load-bearing and mostly sufficient.
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?
Only two sentences, so not bloated, but the first is a long run-on with an awkward aside ('as its page names it') and stacked clauses. The scoping exclusion is buried mid-sentence rather than front-loaded.
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 single-ticker read-only lookup with annotations covering safety and a description covering return contents, an agent has enough to call it correctly. The only gap is disambiguation from the other benchmark-related siblings.
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 the single ticker parameter is documented with an example (JEPI). The description adds no further parameter meaning beyond what the schema already provides, so the baseline of 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?
States a specific operation on a specific resource: measuring one ETF against its own named benchmark index or its own holdings, explicitly excluding a category stand-in. An agent can distinguish it from category/peer comparison tools, though the phrasing ('measures one ETF against, as its page names it') is convoluted enough to slow parsing.
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?
Explicitly scopes the tool to a single ETF and routes model-portfolio benchmarks elsewhere via list_benchmarks. It does not clarify how this differs from close siblings like get_benchmark or compare_to_benchmark, which is the main remaining ambiguity.
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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