Lion Reader

create_tag

Idempotent

Create a tag for grouping subscriptions (apply it with set_subscription_tags). If a tag with that name (ignoring case) already exists, returns it unchanged with created: false; to rename or recolor a tag, use update_tag. Returns the tag and created.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

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

Input Schema

Name	Required	Description	Default
`name`	Yes	Tag name (max 50 characters, unique per user ignoring case)
`color`	No	Optional hex color (e.g., #ff6b6b). Null to remove color.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 4, 2026

TDQS

A4.5/5.0

Behavior4/5

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

The annotations declare idempotentHint=true and destructiveHint=false, but the description explains the actual mechanism: a case-insensitive name match returns the existing tag unchanged with created: false. That is the real behavioral risk an agent needs to know about, and it is stated plainly along with the return shape. It stops short of covering permission or auth requirements, which keeps it from a 5.

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?

Three short sentences, front-loaded with purpose, then the collision semantics, then the sibling redirect, then the return value. Nothing is padding; each sentence carries a distinct fact the agent needs.

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 two-parameter creation tool with no output schema, the description covers purpose, idempotent collision behavior, alternatives, and the shape of the return value. There is no meaningful gap an agent would need filled before calling it.

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 name (max 50, unique per user ignoring case) and color (hex or null to remove). The description restates the case-insensitive uniqueness but adds no syntax or format detail beyond what the schema provides, so the 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 ('Create a tag for grouping subscriptions') and immediately distinguishes it from the sibling that applies tags (set_subscription_tags) and the one that modifies them (update_tag). An agent can pick this tool over its neighbors without opening a 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?

Gives explicit routing: use this to create, use set_subscription_tags to apply, use update_tag to rename or recolor. It also covers the collision case where creation is not needed because the tag already exists, so the when-not condition is stated as well as the when.

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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