Find eToro instruments

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely new behavior: exact-match-only semantics, the ETF exchange-suffix convention, and the argument-exclusivity constraint. It does not cover pagination behavior (pageSize) or empty-result handling, keeping it just below 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?

Four tight sentences: what it does and returns first, then the disambiguation, then the edge-case formatting note, then the constraint. No filler, nothing repeated from annotations.

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, the description compensates by listing the return fields (instrumentId, symbol, displayName, type, exchangeId). Combined with the disambiguation and formatting guidance, an agent has everything needed to invoke this 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 description coverage is only 25%, so the description must carry weight: it explains symbols (exact tickers, with a .L ETF example), instrumentIds, and type-based listing, and forbids combining symbols with instrumentIds. Only pageSize is left unexplained, which the schema's default/max partially covers.

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 (look up / list) with named resources (instruments by ticker symbol, instrument id, or type) and enumerates the returned fields. It explicitly distinguishes itself from the sibling etoro_search_instruments, so an agent can route 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 says this is an exact lookup and names the alternative for name/partial text ('for example apple') — etoro_search_instruments — plus the mutual-exclusivity rule ('Provide symbols or instrumentIds, not both'). Both when-to-use and when-not-to-use are covered.

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