Position in one instrument

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real behavior beyond them: a missing holding returns held=false rather than erroring, and includeSellable=true expands the response with sellable share counts split across T0/T1/T+2 settlement cycles. It does not state error behavior for an invalid symbol, which keeps it short of 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?

Two compact sentences, front-loaded with the primary return semantics and the optional flag's effect. No filler, no restatement of the title.

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 return-value burden and does so for the main cases (holding present, held=false, sellable breakdown). It leaves gaps on failure modes for unknown symbols and on how market selection interacts with symbol lookup.

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 67%: market and symbol are documented in the schema, but includeSellable has no schema description, and the description compensates by explaining exactly what turning it on returns (sellable quantity per settlement cycle). This adds meaning the schema alone does not convey.

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 resource and scope: the holding in ONE instrument, with the held=false outcome named. That single-instrument scope implicitly separates it from get_account_positions, but the description never names that sibling, so differentiation is inferred rather than stated.

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 by 'one instrument' (versus the portfolio-wide get_account_positions), but there is no explicit when-to-use, when-not, or named alternative. The includeSellable=true trigger is the only conditional guidance offered.

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