rust.wiki

Rust blackjack: the best play for a hand, or the whole strategy chart

blackjack_strategy

Read-onlyIdempotent

Rust blackjack: the best play for a hand, or the whole strategy chart. The blackjack page's strategy engine (https://rust.wiki/calculators/blackjack), an exact infinite-deck calculation under Rust's caboose rules: no doubling on a hand with an Ace, one split, 3:2 blackjack, and no dealer peek by default. With hand + dealer: the best play and every option's expected value per 1 scrap bet. Without: the full hard, soft and pairs charts (H hit, S stand, D double, P split) per dealer card, plus the house_edge_pct with perfect play (about 0.82% under Rust's rules). Rust's in-game scrap blackjack (caboose), not real-money gambling.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "blackjack_strategy"
  }
}

Input Schema

Name	Required	Description
`hand`	No	Your first two cards, e.g. `A,7` or `10,6` (2-10, J, Q, K, A). Left out = full chart.
`dealer`	No	The dealer's face-up card (needed with hand).
`dealer_peeks`	No	False = Rust: a dealer blackjack also takes doubles and splits.
`double_after_split`	No	Doubling after a split allowed.
`dealer_hits_soft_17`	No	Rust's caboose dealer hits soft 17 (since about Feb 2024).

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 14, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the description's real contribution is domain-fidelity context: exact infinite-deck calculation, caboose rules (no double on an Ace hand, one split, 3:2 blackjack, no dealer peek), and the ~0.82% house edge. This is meaningful beyond structured fields, though it does not discuss response format size for the full-chart mode.

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 the core purpose, then a parenthetical rules block, then mode behavior. Dense but nearly every clause carries information; the URL and rule list are the only slightly padded segments.

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?

With no output schema, the description carries the return-value burden and does so: it names `best`, per-option expected values per 1 scrap bet, the `hard`/`soft`/`pairs` charts with an H/S/D/P legend, and `house_edge_pct`. An agent knows both what it gets and how to read it.

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

Parameters4/5

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

Schema coverage is 100%, so baseline is 3, but the description adds rule-level meaning: the house rules behind `dealer_peeks`, `double_after_split`, and `dealer_hits_soft_17` are spelled out (caboose rules, dealer hits soft 17 since Feb 2024). It stops short of explaining how toggling them changes results.

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?

Names a specific verb and resource — return the best play for a hand or the full strategy chart — and immediately distinguishes the two modes via the `hand` + `dealer` condition. An agent can tell exactly what this returns without opening the schema.

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

Usage Guidelines5/5

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

Explicitly states the two operating modes: 'With `hand` + `dealer`: the `best` play…' versus 'Without: the full `hard`, `soft` and `pairs` charts.' The schema's 'Left out = full chart' reinforces this. No inference needed to choose behavior.

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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