cozyvtt-mcp

Saved Roll Update

saved_roll_update

Destructive

Update a saved roll's name or expression in your CozyVTT campaign. Provide the roll's ID and at least one new value; validation and ownership checks are handled automatically.

Instructions

Change the name or expression of your Saved Roll in this campaign. Use saved_roll_list to find its ID; use dice_roll to execute it. Supply at least one field; null leaves that field unchanged. Upstream validates expressions and enforces per-user/per-campaign ownership. Replacing values does not roll dice; repeated writes may change update metadata, so full-operation idempotency is not guaranteed. Returns {ok:true,data} on success; tool-body failures return {ok:false,error} with optional diagnostic data. Argument-schema errors are MCP errors.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	No	Replacement display label, trimmed to 1..60 characters; null preserves it. At least one of name/expression is required.
`macro_id`	Yes	Existing Saved Roll ID owned by the current user in this campaign.
`expression`	No	Replacement expression, trimmed to 1..200 characters and parsed upstream; null preserves it. At least one field is required.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Addedv0.3.0Sep 20, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Beyond annotations, it discloses that replacing values does not roll dice, that repeated writes may change update metadata and thus full idempotency is not guaranteed, and that upstream validates expressions and enforces ownership. It also explains the success/error return envelope, which is valuable context not present in the annotations.

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 dense but well-organized: action first, then sibling routing, then update semantics, then behavioral caveats, then return format. Every sentence earns its place and no unnecessary filler is present.

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?

For a partial-update mutation tool, this is complete: what it updates, how to find the target ID, what happens with nulls and multiple writes, ownership validation, and both success and failure response shapes. The presence of an output schema does not create a gap because the description covers the relevant behavior.

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 name, macro_id, and expression meanings plus null-count semantics. The description adds the useful pointer to use saved_roll_list to find macro_id, but otherwise largely restates what the schema already covers.

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 uses a specific verb ('Change') and names the exact resource and fields ('name or expression of your Saved Roll in this campaign'). It also distinguishes itself from related siblings by pointing to saved_roll_list for ID lookup and dice_roll for execution.

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?

It explicitly tells the agent when to use this tool ('Change the name or expression') and names alternatives with their conditions: use saved_roll_list to find the ID and dice_roll to execute. It also clarifies the partial-update contract: supply at least one field, null leaves it unchanged.

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