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Public.com MCP Server

Public.com MCP Server

Official
by PublicDotCom
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

preflight_short_order

Read-only

Estimate commission, fees, and buying power impact for a short-sale equity order before placing it; does not execute the order.

Instructions

Estimate costs for a short-sale equity order before placing it.

Returns estimated commission, fees, and buying power impact. Does NOT place an order.

Args: symbol: Ticker symbol to short (e.g. "AAPL"). quantity: Number of shares to short. order_type: MARKET, LIMIT, STOP, STOP_LIMIT, MARKET_ON_CLOSE or LIMIT_ON_CLOSE. Default is MARKET. The on-close types execute at the closing auction. time_in_force: DAY or GTD. Default is DAY. limit_price: Required for LIMIT, STOP_LIMIT and LIMIT_ON_CLOSE orders. stop_price: Required for STOP and STOP_LIMIT orders. expiration_time: Required when time_in_force is GTD. ISO 8601 format. equity_market_session: CORE or EXTENDED. account_id: Account ID. Optional if PUBLIC_COM_ACCOUNT_ID is set.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "symbol": "<symbol>",
      "quantity": "<quantity>"
    },
    "name": "preflight_short_order"
  }
}

Input Schema

NameRequiredDescriptionDefault
symbolYes
quantityYes
account_idNo
order_typeNoMARKET
stop_priceNo
limit_priceNo
time_in_forceNoDAY
expiration_timeNo
equity_market_sessionNo

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.3.1

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true. The description adds substantive context beyond that: what is estimated (commission, fees, buying-power impact) and the crucial assurance that no order is placed. It does not cover error conditions or account prerequisites beyond the env-var fallback.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with purpose and the no-placement warning, then a compact Args block. Each argument line carries information, though the format is closer to a docstring dump than tightly integrated prose.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 9-parameter tool with zero schema coverage and an existing output schema, the definition supplies everything an agent needs: the conditional parameter rules, order-type semantics, default values, and the account_id fallback. Return values are already covered by the output schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description bears the full burden, and it delivers: it documents every parameter and the conditional requirements (limit_price for LIMIT/STOP_LIMIT/LIMIT_ON_CLOSE, stop_price for STOP/STOP_LIMIT, expiration_time for GTD, account_id optional when the env var is set). It also explains on-close execution at the closing auction, which is not in the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Estimate costs for a short-sale equity order') and explicitly contrasts with the sibling that places orders ('Does NOT place an order', 'before placing it'). An agent can distinguish it from place_short_order 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.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description says the tool is to be used before placing, which implies pairing with place_short_order, and explicitly excludes placement. It stops short of naming the alternative tool or stating when not to preflight at all.

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

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