Get an eToro investor's public data

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

Goes well beyond the annotations by disclosing partial-failure behavior ('A section that fails is reported in `errors` without losing the others'), the read-only scope ('it places nothing'), and an explicit prompt-injection warning to treat investor free text as untrusted data. These are non-obvious behavioral traits an agent must know to use the result safely.

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?

Front-loaded with the core purpose and section semantics, and every sentence is broadly useful. The disclaimer sentences ('Past performance is not a forecast…') and 'Other investors' public data from eToro' are slightly redundant filler that dilute an otherwise tight paragraph.

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 carries the return-value burden and does so: it describes the content of every section, the default selection, and how errors are surfaced. An agent has everything needed to call this correctly and interpret partial results.

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 only 33%, and the description compensates meaningfully: it names and defines all five `sections` values (including return-shape details like portfolio 'grouped by instrument and sorted by weight, top 25') and ties `period` to tradeinfo statistics. It does not explain interaction effects, e.g. that `period` is meaningful only when tradeinfo is selected.

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+resource+scope: 'Public information about one investor by username', which cleanly distinguishes it from the plural-search sibling etoro_search_investors. It then enumerates exactly what each readable section returns, so an agent knows what it will get without opening the 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?

Gives clear guidance on when to use each `sections` value and what the defaults are, plus the scope limit ('Public data only; it places nothing'). However, it never names an alternative (e.g. etoro_search_investors) for the case where the caller does not already know a username, even though username is required and pattern-constrained.

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