Read E*TRADE positions and cash

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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), and the description adds real behavioral detail beyond them: marking at last trade with trade date, an explicit omission rule for positions lacking a symbol or usable mark, and the trailing JSON block shape. It does not cover pagination or per-account limits, but the filtering behavior is a genuinely useful disclosure.

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, front-loaded with what is returned, followed by the key integration detail and then the caveat. Each sentence earns its place; only the marketing-ish phrasing 'without the user retyping it' is mildly redundant.

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 per-position mark, the cash figure, the trailing rebalance-shaped JSON block, and the omission rule. Adequate for a single-parameter read tool, though it does not address multiple-account selection or staleness of marks.

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 schema already explains that accountIdKey is the opaque key from etrade_accounts and that the human-readable number is rejected. The description says nothing about the parameter, so it adds no meaning beyond the schema — baseline 3 is correct when structured data does the work.

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: 'current holdings and investable cash for one E*TRADE account', and clarifies the marking semantics (last trade with its date). It does not explicitly distinguish itself from the sibling etrade_balances, so an agent must infer the boundary, but the purpose itself is unambiguous.

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?

Usage is implied through the integration note — the response is shaped for plan_rebalance's holdings argument, so this is what feeds a rebalance. However there is no explicit when-to-use statement, no 'use etrade_balances instead when X', and no prerequisite guidance. The context is inferable but not stated.

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