partial_close_positionClose a specified portion of an open futures position at market price to reduce exposure and lock in partial profits while keeping the rest active.
Close part of a position at market (scale out).
| Name | Required | Description | Default |
|---|---|---|---|
| size | Yes | ||
| reason | No | ||
| accountId | Yes | Trading account ID from list_accounts. | |
| contractId | Yes | Contract ID, e.g. "CON.F.US.MNQ.Z25". Get it from search_contracts. |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already convey that this is destructive and not read-only, and the description adds that execution happens at market rather than as a limit order. It does not contradict the annotations, but it does not disclose additional behavioral details such as partial-fill risk, impact on remaining position, or requirements like an existing position.
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?
The description is a single, efficient sentence with no filler. Key qualifiers ('part', 'at market', 'scale out') are front-loaded and every word adds value.
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 destructive trading action with no output schema, the description is too thin: it does not state expected response behavior, size limits, or prerequisites such as an existing open position. The schema covers param sources but not the semantics of the size and reason fields, leaving an agent under-equipped to call 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?
Schema descriptions cover only accountId and contractId, leaving size and reason undocumented, and the tool description does not compensate. 'Part of a position' hints that size is the partial quantity, but the description does not clarify size units, constraints relative to the open position, or the purpose of reason.
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?
The description uses a specific verb ('Close'), resource ('position'), and qualifiers ('part', 'at market', 'scale out'), making the purpose immediately clear. It also distinguishes itself from the sibling close_position by explicitly limiting the action to a partial close.
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?
The phrase 'Close part of a position' implies the use case of scaling out versus fully closing, but it does not explicitly name close_position or state when not to use this tool. The guidance is present only by implication rather than as an explicit routing rule.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.