find_etfs_holding_stock

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and does meaningful work: it discloses the default universe size (~365 ETFs), that results are sorted by weight descending, and that coverage is limited to 'disclosed top holdings' (i.e., partial data). It omits failure modes such as what happens for an unknown ticker or an empty result set, so it stops short of a 5.

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, zero filler, with the core purpose and the sorting/universe semantics front-loaded before the sibling routing at the end.

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?

An output schema exists, so return values need not be explained. Between the description's scope, sorting, universe size, and explicit alternative, plus a fully covered parameter schema, an agent has everything needed to select and invoke it correctly.

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%, so the schema already documents all three parameters and the baseline is 3. The description adds useful semantic context beyond the schema by stating the default universe is ~365 ETFs and that a custom list substitutes for it, clarifying the intent of custom_etf_universe.

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 verb and resource ('Reverse-lookup: find ETFs that hold a given stock') plus the scope of the lookup ('disclosed top holdings'), which immediately separates it from etf_holdings and search_etfs.

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 names the alternative sibling and the condition that selects it: 'For a version that also reports each ETF's expense ratio and size, use stock_exposure_summary.' This is exactly the when/when-not routing an agent needs.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.