A2UI Atomic Catalog

render_reading_to_slack

Post a kept reading into Slack as real, native Block Kit — the continuity proof: generate here, save it, and the SAME content reopens in Slack, not a link back to a renderer. Requires the caller's Slack account to already be linked (/a2ui link in Slack) and only works on an authenticated connection — it posts to a real workspace using a shared bot token.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

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

Input Schema

Name	Required	Description	Default
`id`	No	Reading id from list_readings. OMIT for the most recent one.
`channel`	No	Slack channel to post to. Default #general.

Output Schema

Name	Required	Description
`ok`	No	True when the post succeeded.
`note`	No	Guidance for the caller.
`title`	No	Reading title.
`reason`	No	Why nothing was posted.
`degraded`	No
`slack_ts`	No	Slack message timestamp.
`available`	No	False without a signed-in reader.
`posted_as`	No	Linked Slack account.
`posted_to`	No	Slack channel.
`truncated`	No
`reading_id`	No	Reading id.
`atoms_skipped`	No	Atom types with no Slack mapping.
`atoms_compiled`	No	Atoms posted.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 10, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already declare the write/open-world/non-idempotent profile, so the description's added value is the authorization prerequisite (account linking) and the fact that it posts into a real workspace using a shared bot token — context an agent cannot get from the schema or annotations. It stops short of describing side effects like threading, duplicates on repeat calls, or failure modes, so a 4 rather than 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.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The core action and the native-Block-Kit distinction are front-loaded, and the auth requirements follow as supporting detail. Some framing language ("the continuity proof: generate here, save it") is promotional rather than operational, which costs a point.

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?

With only two optional parameters, full schema coverage, an output schema, and annotations covering the safety profile, the remaining burden is auth and destination behavior — both of which the description addresses. The absence of explicit repeat-call or failure behavior is a minor gap for an open-world write tool.

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%, and the schema already explains that `id` comes from list_readings with omission meaning the most recent, and that `channel` defaults to #general. The description adds no further parameter meaning, 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?

The description gives a specific verb and resource — "Post a kept reading into Slack as real, native Block Kit" — and immediately frames the distinguishing property versus siblings: the content reopens natively in Slack rather than as a link back to a renderer, which separates it from export_reading or the surface-URL tools.

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?

It states clear preconditions: the caller's Slack account must already be linked via `/a2ui link`, and the connection must be authenticated to a real workspace with a shared bot token. It implicitly contrasts with link-based rendering, but does not name an explicit alternative tool or state when NOT to use this one, keeping it short of a 5.

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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