Lion Reader

add_to_collection

Idempotent

Add articles to a collection (find its ID with list_subscriptions, or make one with create_collection). Any article the user can see works, feed entry or saved article; it stays in its own feed too, sharing read and starred state. A collection holds at most 10000 articles. Returns the IDs newly added; IDs already present or not visible are skipped. Fails with a not-found error if the collection isn't the user's. To order the collection, use set_collection_positions.

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": {
      "collectionId": "<collectionId>",
      "entryIds": "<entryIds>"
    },
    "name": "add_to_collection"
  }
}

Input Schema

Name	Required	Description	Default
`entryIds`	Yes	Entry IDs
`collectionId`	Yes	The collection's subscription ID (list_subscriptions shows collections with type 'collection')

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 4, 2026

TDQS

A4.9/5.0

Behavior5/5

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

Annotations already declare a non-read-only, non-destructive, idempotent mutation, and the description adds substantial context beyond them: the 10,000-article collection cap, that entries remain in their own feed and share read/starred state, that returns are newly-added IDs only, and that a not-found error occurs for collections the user doesn't own.

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 layers prerequisites, constraints, return semantics, and the ordering alternative in compact sentences with no redundancy.

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 mutation with no output schema, the description covers input sourcing, capacity limits, skip behavior, return values, and failure mode — everything needed to call it correctly.

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 earns extra by clarifying that entryIds may be either feed entries or saved articles ('any article the user can see'), which the schema's bare 'Entry IDs' label does not convey.

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 articles to a collection' — which an agent can immediately separate from remove_from_collection, create_collection, and delete_collection in the sibling list.

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 routes the agent: find the ID with list_subscriptions, create one with create_collection, and use set_collection_positions for ordering. Both prerequisites and the alternative for ordering are named, leaving little to infer.

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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