Embers: Tabletop RPG Toolkit

Add a ruleset leg to a campaign

play_add_campaign_leg

Add a new active leg to a campaign for the given ruleset, letting the same campaign (same sessions, players, and history) also run under that ruleset. The new leg starts empty — no rules, items, spells, or characters; fill it with the add tools. One leg per ruleset: play answers 409 if a leg for this ruleset already exists. Caller must be the campaign owner or an accepted gamemaster; ordinary players get 403.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`ruleset`	No	Ruleset code for the new leg; list_rulesets returns the codes this account can use. Required. One leg per ruleset — play answers 409 if the campaign already has a leg for this ruleset, 400 for an unknown code, and 403 for a ruleset this account is not entitled to.
`campaignId`	Yes	Campaign id.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 27, 2026

changedInput schema / properties / ruleset / description

Previous value: -"Ruleset for the new leg. Required. One leg per ruleset — play answers 409 if the campaign already has a leg for this ruleset."New value: +"Ruleset code for the new leg; list_rulesets returns the codes this account can use. Required. One leg per ruleset — play answers 409 if the campaign already has a leg for this ruleset, 400 for an unknown code, and 403 for a ruleset this account is not entitled to."

removedInput schema / properties / ruleset / enum

Removed value: -[
-  "5th Edition",
-  "5e24",
-  "PFRPG",
-  "PFRPG2",
-  "PF Playtest",
-  "Savage Worlds",
-  "Savage Embers",
-  "Solarian Conflict",
-  "Embers RPG",
-  "Universal",
-  "Fate Core",
-  "Fate Accelerated"
-]

addedInput schema / properties / ruleset / minLength
```
Added value: +1
```

First observedSep 21, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Goes well beyond the annotations by disclosing that the new leg starts empty (no rules/items/spells/characters), that duplicate ruleset legs yield a 409, and that the caller must be the owner or an accepted gamemaster or receive a 403. These are exactly the preconditions and side effects an agent needs for a non-idempotent mutation.

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?

Front-loads the action, then the empty-leg behavior, then the constraint and auth in a compact, well-ordered three-sentence block with no wasted text.

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 an output schema present, return values need no explanation; the description covers authorization, emptiness, and the duplicate-ruleset error path, leaving nothing an agent needs to call this correctly.

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 description coverage is 100%, so the schema already documents both parameters including the 400/403/409 error conditions for the ruleset code. The description only restates 'for the given ruleset' and the 409, adding little beyond the schema; baseline 3 applies.

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 ('Add a new active leg to a campaign for the given ruleset') and explains the concept of a 'leg' as the same campaign running under another ruleset. This clearly distinguishes it from the sibling add tools (play_add_campaign_rule/item/spell/character) which fill the leg rather than create it.

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?

Explains the scenario for the call and routes the agent onward ('fill it with the add tools'), and gives the selection constraint 'one leg per ruleset'. It does not name an explicit alternative tool, but there is no direct competing tool, so the context is clear.

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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