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

Annotations already mark the call read-only and non-destructive. The description adds useful behavioral context beyond annotations: only active ETFs are searched, identity is sourced from the authoritative reference directory, and assets/holdings are included only when the linked NPORT-P series is available.

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 sentences, each with a distinct job: state the search scope, explain data provenance/availability, and route to relevant siblings. There is no filler or repetition of schema field names beyond what is useful.

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 search tool with full schema coverage, the description covers selection, query semantics, source reliability, and follow-up tools. It omits exact return-field details, but with no output schema declared, the prose gives enough for an agent to 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 carries parameter docs for query and maxResults. The description adds meaning not present in the schema by specifying 'exact' matching and the 'active' filter, plus clarifying that returned identity/assets/holdings have different data sources.

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 opens with a specific verb and resource: 'Search active exchange-traded funds and products by exact ticker, fund name, or sponsor.' It clearly scopes the tool to ETFs and products and distinguishes its role from downstream siblings like GetEtfProfile and GetEtfHoldings.

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 gives concrete routing guidance: 'Use GetEtfProfile for analysis or GetEtfHoldings for a paged portfolio.' It does not explicitly contrast with SearchFunds or state when not to search, so it lacks an exclusion, but the intended context is clear.

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