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ably

by io.usefulapi

Publish a message to a channel

ably_publish_message
Destructive

WRITE: publish a message to a channel. Every connected subscriber receives it in real time. This is a real, outward-facing side effect — confirm the channel and payload before calling. REST: POST /channels/{channel}/messages.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYesMessage payload (string; send JSON as a stringified value).
nameNoOptional event name for the message.
channelYesChannel name to publish to, e.g. 'chat:room1'.
clientIdNoOptional clientId to attribute the message to.

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already mark this as destructive; the description adds beyond that by stating it is an outward-facing side effect, that all connected subscribers receive the message in real time, and that confirmation is needed before calling. This meaningfully enriches the annotation without contradicting it.

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, each earning its place: the operation, the real-time effect, and the caution. The WRITE prefix is front-loaded and the REST endpoint is a useful compact addition.

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?

For a four-parameter write operation with a destructive annotation, the description covers the key behavioral context: it is a real side effect, delivery is real-time to subscribers, and the caller should verify inputs. No output schema exists, but the success semantics are straightforward enough that omitting return details is acceptable.

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 documents channel, data, name, and clientId adequately. The description adds no new parameter-level detail, but the baseline of 3 applies because the schema carries the full meaning.

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 ('publish') and resource ('message to a channel'), and marks it clearly as a WRITE operation. It also names the observable consequence (subscribers receive it in real time), which distinguishes it from the sibling read/list 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?

The WRITE label and side-effect warning make the intended use clear: this is for publishing, not retrieving data. It doesn't explicitly name excluded alternatives, but among an all-read sibling set the usage context is unmistakable and the caution to confirm channel and payload is practical guidance.

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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TDQS

A4/5.0
Disambiguation5/5

Every tool targets a distinct resource and action: account-level stats, app-level stats, channel details, history, presence, presence history, service time, and each control-plane listing (apps, keys, namespaces, queues, rules) are clearly separated. The only potentially confusing pair is account stats vs app stats, but their descriptions explicitly differentiate account-wide vs API-key-scoped usage.

Naming Consistency5/5

All tools use a uniform 'ably_' prefix followed by a consistent verb_noun pattern: get_ for single resources, list_ for collections, publish_message for the write action, and whoami for token details. There are no mixed casing styles or inconsistent verb choices.

Tool Count5/5

Fifteen tools is within the ideal range and each one covers a meaningful Ably capability, from control-plane inspection to channel data retrieval and publishing. The count feels justified given the breadth of Ably's API surface, with no redundant or filler tools.

Completeness3/5

The read side is well covered: stats, channel details, history, presence, and control-plane listings all have dedicated tools, and message publishing provides one write path. However, there are no create/update/delete operations for apps, keys, namespaces, queues, or rules, so lifecycle management is largely absent and an agent could not perform common administrative workflows.

Resources