Read E*TRADE balances

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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds useful behavioral context by enumerating the returned data (settled vs unsettled, buying power, open margin calls), which tells the agent what state is exposed. It stops short of noting auth requirements, rate limits, or freshness of the balance snapshot.

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, no waste. It front-loads the content enumeration and then immediately hands off the disambiguation rule, which is exactly the ordering an agent needs.

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 read-only, single-parameter tool with a fully specified schema and no output schema, this is complete: content scope, account scoping, and the sibling distinction are all present, and the safety profile comes from annotations.

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% and the single accountIdKey parameter is thoroughly documented in the schema itself (opaque key vs account number, API rejects the number). The description adds no parameter detail beyond the schema, so the baseline 3 applies.

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 ('Read E*TRADE balances') and then enumerates exactly what the payload contains: cash available, settled vs unsettled, buying power, margin balance, market value, margin calls. It explicitly distinguishes itself from etrade_positions, so an agent can route correctly 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 an explicit selection rule — use this for 'what do I have to deploy?' versus etrade_positions for 'what do I hold?' — naming the sibling alternative and the condition that picks between them. Nothing is left to inference.

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