fetch_account_summary

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

With no annotations, the description carries the full burden and does so well: it discloses the fail-closed 502 `authoritative_margin_unavailable` behavior, instructs a retry rather than misreading the error as an empty account, defines `withdrawable` (engine-authoritative free margin floored at zero, never negative), and notes the API-credential requirement. This is exactly the kind of context annotations would otherwise supply.

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, then the differentiating detail and the failure-mode warning. The prose is dense and occasionally parenthetical-heavy, but every sentence carries operational value; nothing is padding.

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?

No output schema exists, so the description must explain return values — and it does, naming the equity/margin/PnL rollup and precisely defining `withdrawable`. Combined with the 502 failure disclosure and credential note, an agent has everything needed to call and interpret 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?

The tool takes zero parameters, which sets the baseline at 4; there is nothing in the schema for the description to clarify or compensate for. The descriptions of returned fields (`withdrawable`) are a bonus but belong to transparency, not parameter semantics.

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 (get) and resource (authenticated account's portfolio summary), enumerates its contents (equity, margin usage, PnL rollup), and explicitly positions it against the sibling `fetch_balance` as a richer view. An agent can select it without opening any 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 names the alternative (`fetch_balance`) and characterizes when this tool wins (richer portfolio view). It stops short of stating when NOT to use it or spelling out a decision rule, but the comparative framing is clear.

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