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

Despite the readOnlyHint annotation, the description explicitly states 'Read-only' and adds a crucial caveat about provider holdings being partial top-holdings samples, warning that coverage is not guaranteed. This goes beyond the annotation and helps the agent set correct expectations.

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, zero filler. The first sentence front-loads the action and return types; the second provides a necessary caveat. Every clause contributes meaning.

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?

Given the output schema exists, return values need no description. The description covers inputs (two to ten ETFs), the algorithm (weighted overlap), the key caveat (partial holdings), and the safety profile (read-only). This is sufficient for an agent to select and invoke the tool 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 50% (only 'tickers' has a description). The description reinforces the range of tickers but completely omits any explanation of 'topSharedLimit' (e.g., that it controls the number of largest duplicate exposures returned). The description does not compensate for the undocumented parameter.

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 a specific verb ('Compare'), a specific resource ('ETFs'), and a precise scope ('two to ten'), then enumerates the exact outputs (pairwise shared holdings, weighted overlap, etc.). This clearly distinguishes it from sibling tools like compare_etfs, which likely covers broader comparisons.

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?

The description implies usage for overlap analysis and clarifies the number of ETFs, but it does not explicitly mention when to prefer this tool over alternatives like compare_etfs, nor does it state exclusions or prerequisites. The context is present but not differentiated from siblings.

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