D&D 5e SRD Oracle

Start Battle

start_battle

Destructive

Start a D&D battle session from finalized character builds and SRD stat blocks. Provide initiative scores for every combatant, admit retained companions, and begin turn-order combat.

Instructions

Start a battle session from finalized Character Builds and selected SRD Stat Blocks. When list_stat_blocks exposes alternative Sizes, provide one authored size on that Stat Block combatant. The caller must provide Initiative scores for every combatant; choose initialSetup to keep the SDK-owned Initiative setup open for the battle_lifecycle surface.

Input Schema

TableJSON Schema

Name	Required	Description
`battleId`	Yes	Caller-chosen durable battle id.
`playSessionId`	Yes	Play Session handle returned by create_play_session for follow-up stateful calls in the same local process or authenticated account.
`initiativeMode`	Yes	Use direct for an already supplied Initiative score or initialSetup to retain the SDK-owned setup for supported swaps and finalization. This field is required.
`initialCombatants`	Yes	Non-empty initial combatant roster. Each combatant comes from a finalized character session or an ordinary SRD Stat Block.
`companionAdmissions`	Yes	Explicit retained-companion admissions. Use an empty array when no retained companion enters the battle.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 21, 2026

TDQS

A4.2/5.0

Behavior3/5

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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutating nature is known. The description adds useful stateful context about keeping the SDK-owned Initiative setup open for the battle_lifecycle surface, but does not describe specific side effects or what is destroyed, which is acceptable given the annotation bar is lower.

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?

The description is three sentences with no filler: purpose, conditional Size guidance, and Initiative/mode requirements are each front-loaded and useful. Every sentence earns its place.

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?

For a stateful creation tool, it covers prerequisites, source types, Initiative requirements, and mode consequences, and an output schema exists so return values are not a gap. It omits companionAdmissions as a third admission path, which the schema covers but the prose does not surface.

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 the baseline is 3; the description adds cross-tool meaning by tying Size selection to list_stat_blocks alternatives and clarifying that Initiative is required for every combatant and why initialSetup matters. It does not mention companionAdmissions, but the schema already fully documents that parameter.

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?

The description names a specific action (start), a specific resource (battle session), and the two valid source types (finalized Character Builds and SRD Stat Blocks). It clearly distinguishes itself from mutation/read siblings like end_turn, end_battle, and read_battle_state.

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 gives clear context: it requires finalized characters, selected stat blocks, caller-provided Initiative scores, and explains when to use initialSetup. It does not explicitly enumerate when not to use this tool or contrast it directly with sibling tools, but it is strong enough for the starting-battle scenario.

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