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PlayAINetwork

Polymarket MCP Server

placeLimitOrder

Place a limit order on prediction markets with specified price, size, and side. Supports Good-Till-Cancelled and Good-Till-Date order types.

Instructions

Place a limit order (Good Till Cancelled / Good Till Date)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
sideYesOrder side - BUY or SELL
sizeYesSize in shares to trade
priceYesPrice per share (between 0 and 1)
outcomeNoMarket outcome to bet on - YES or NO (required if using marketSlug)
tokenIDNoDirect token ID for the market outcome (alternative to marketSlug+outcome)
tickSizeNoTick size for the market (auto-detected if using marketSlug)
orderTypeYesOrder type - GTC (Good Till Cancelled) or GTD (Good Till Date)
marketSlugNoMarket slug from the URL (e.g., 'fordow-nuclear-facility-destroyed-before-july'). Either marketSlug+outcome OR tokenID must be provided
expirationMinutesNoExpiration time in minutes (only for GTD orders)
Behavior2/5

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

No annotations; description only states action and order types. Does not disclose that limit orders may not fill, order book behavior, or any side effects. Lacks depth.

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

Conciseness5/5

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

Extremely concise single sentence with no filler. Every word is necessary.

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

Completeness2/5

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

With 9 parameters, no output schema, and no annotations, the description is too sparse. Missing success/error behavior, required combinations (marketSlug+outcome vs tokenID), and order lifecycle details.

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

Parameters3/5

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

Schema coverage is 100% with descriptions for all 9 parameters. Description adds no extra meaning beyond schema, baseline 3 appropriate.

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

Purpose4/5

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

Clearly states 'Place a limit order' with order types GTC/GTD, distinguishing from placeMarketOrder. However, no explicit differentiation from siblings.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

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

No guidance on when to use vs placeMarketOrder, no prerequisites or context provided. Agent must infer from name alone.

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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