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

Goes well beyond the readOnly/idempotent annotations to disclose non-obvious behavior: exact-match-only semantics with refusals that explain why, a refusal implying ETFIQ does not publish the fund, ticker-change resolution, closed-fund pages with a closure date, and SEC-filed non-trading entities landing in a separate 'filed' bucket with counts rather than results. This is exactly the behavioral context annotations cannot carry.

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?

Purpose and lookup keys are front-loaded, and nearly every clause contributes distinct behavior (refusals, ticker changes, closures, filed-only entities). Some sentences are heavily nested and the final clause about 'how many are filed and how many trade' is dense, but there is no filler.

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?

With no output schema and no param documentation, the description compensates well on edge-case return behavior but says nothing about the shape of a normal result, what 'limit' bounds, or what 'desk' scopes to. Adequate for picking the tool, incomplete for calling it confidently.

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 description coverage is 0% and three parameters exist, yet the description only implicitly characterizes 'query' (ticker, fund name, or a word from the name). Neither 'desk' nor 'limit' is mentioned anywhere, so two of three parameters are undocumented in both the schema and the description.

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 and resource ('Find US listed ETFs') plus the three accepted lookup keys (ticker, fund name, word from the name). It also distinguishes itself from the sibling that continues the workflow ('etf_profile then takes the ticker it returns'), so an agent can separate search from profile without opening either schema.

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 frames the tool as the entry point for loosely remembering a fund name and names etf_profile as the follow-up, which is real routing guidance. It does not compare against other candidates like etf_screen or the broader etf_* lookups, and gives no exclusion criteria, so it stops short of a 5.

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