Prediction Markets Quant

Calculate EV Edge

calculate_ev

Read-only

Use for "is this contract mispriced" and "what is my edge". Give a Kalshi or Polymarket price in cents and your own probability; returns the % expected-value edge and a BUY / SELL / SKIP read.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`marketPrice`	No	Current contract price in cents (1–99), equal to the implied probability in %. Required for a real answer. Accepts 55, "55%", "55¢", "$0.55", 0.55 or American odds (+120 / -150) — all read as 55%.
`yourProbability`	No	Your own estimate of the true probability the contract resolves YES, in % (0–100). Required for a real answer. Accepts 55, "55%", "55¢", "$0.55", 0.55 or American odds (+120 / -150) — all read as 55%.

Output Schema

TableJSON Schema

Name	Required	Description
`signal`	No	BUY / SELL / SKIP.
`edge_pp`	No	Your probability minus the price, pp.
`sources`	No
`edge_pct`	No	Expected-value edge, %.
`tell_user`	No	Show this sentence to the user first.
`timestamp`	No
`needs_input`	No
`example_call`	No
`data_freshness`	No
`interpretation`	No	Plain-English read.
`market_price_cents`	No	Price used, cents.
`your_probability_pct`	No	Probability used, %.

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 15, 2026

removedInput schema / properties / marketPrice / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "string"
-  }
-]

addedInput schema / properties / marketPrice / type
```
Added value: +[
+  "number",
+  "string"
+]
```

removedInput schema / properties / yourProbability / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "string"
-  }
-]

addedInput schema / properties / yourProbability / type
```
Added value: +[
+  "number",
+  "string"
+]
```

Changed3 schema fields changedOct 1, 2026

changedInput schema / properties / marketPrice / description

Previous value: -"Current contract price in cents (1–99), equal to the implied probability in %. Accepts 55, \"55%\", \"55¢\", \"$0.55\", 0.55 or American odds (+120 / -150) — all read as 55%."New value: +"Current contract price in cents (1–99), equal to the implied probability in %. Required for a real answer. Accepts 55, \"55%\", \"55¢\", \"$0.55\", 0.55 or American odds (+120 / -150) — all read as 55%."

changedInput schema / properties / yourProbability / description

Previous value: -"Your own estimate of the true probability the contract resolves YES, in % (0–100). Accepts 55, \"55%\", \"55¢\", \"$0.55\", 0.55 or American odds (+120 / -150) — all read as 55%."New value: +"Your own estimate of the true probability the contract resolves YES, in % (0–100). Required for a real answer. Accepts 55, \"55%\", \"55¢\", \"$0.55\", 0.55 or American odds (+120 / -150) — all read as 55%."

removedInput schema / required

Removed value: -[
-  "marketPrice",
-  "yourProbability"
-]

Changed1 schema field changedSep 29, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "additionalProperties": {},
+  "properties": {
+    "data_freshness": {},
+    "edge_pct": {
+      "description": "Expected-value edge, %."
+    },
+    "edge_pp": {
+      "description": "Your probability minus the price, pp."
+    },
+    "example_call": {},
+    "interpretation": {
+      "description": "Plain-English read."
+    },
+    "market_price_cents": {
+      "description": "Price used, cents."
+    },
+    "needs_input": {},
+    "signal": {
+      "description": "BUY / SELL / SKIP."
+    },
+    "sources": {},
+    "tell_user": {
+      "description": "Show this sentence to the user first.",
+      "type": "string"
+    },
+    "timestamp": {
+      "type": "string"
+    },
+    "your_probability_pct": {
+      "description": "Probability used, %."
+    }
+  },
+  "type": "object"
+}

First observedSep 6, 2026

TDQS

A3.8/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safe, side-effect-free nature is covered structurally. The description adds useful domain scope by tying the tool to Kalshi and Polymarket prices and previews the verdict output, but says nothing about rate limits, accuracy assumptions, or edge cases (e.g. price at 0/100).

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?

Two tight sentences: the trigger/question framing is front-loaded, followed by the inputs and the returned outputs. No filler, no repetition of the schema.

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

Completeness4/5

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

With an output schema present the description need not explain the return payload, and with 100% schema coverage it need not document parameters. It covers purpose, trigger, and output shape. The remaining gap is cluster-level: no pointer to kelly_size for follow-on position sizing.

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% and the schema descriptions already enumerate every accepted input format (55, "55%", "55¢", "$0.55", 0.55, American odds). The description only paraphrases this as "in cents and your own probability", which is actually narrower than the schema. Baseline 3 is correct when the schema carries the semantics.

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?

The description states a specific function: take a market price plus the user's own probability and return the % EV edge and a BUY/SELL/SKIP read. That is a clear verb+resource with an output preview. It does not distinguish itself from the related sibling kelly_size, which an agent might reasonably confuse it with.

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?

"Use for 'is this contract mispriced' and 'what is my edge'" gives an explicit when-to-use trigger in the user's own vocabulary. It offers no exclusions and never names the obvious downstream alternative (kelly_size for sizing once edge is known), so sibling routing is left to inference.

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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