ably_get_presence_historyRetrieve historical presence events (enter/leave/update) for a channel. REST: GET /channels/{channel}/presence/history.
| Name | Required | Description | Default |
|---|---|---|---|
| end | No | Latest event time, ms since epoch (inclusive). | |
| limit | No | Max events (<=1000). Default 100. | |
| start | No | Earliest event time, ms since epoch (inclusive). | |
| channel | Yes | Channel name. | |
| direction | No | forwards or backwards (default backwards). |
Changes observed during successful MCP inspections.
Input schema / $schemaPrevious value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds the REST endpoint mapping and the event taxonomy, which is mild extra context, but says nothing about retention windows, result ordering defaults, or how far back history is available.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences with the purpose front-loaded and no filler. The REST endpoint line is marginally useful for mapping to API docs but is the least essential part.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a read-only, single-channel history query with 100% schema coverage and a readOnlyHint, the definition covers what the agent needs to invoke it. With no output schema present, the description could have sketched the returned event shape (timestamps, client ids, connection ids), which is the one remaining gap.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so channel, start, end, limit, and direction are fully documented in the schema itself. The description only echoes the channel path segment and adds no format, default, or interaction semantics beyond the schema. Baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource ('Retrieve historical presence events ... for a channel') and even enumerates the event kinds (enter/leave/update), which separates it from ably_get_presence (current state) and ably_get_channel_history. It stops short of naming those siblings explicitly, so an agent must infer the distinction.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The word 'historical' implies when this tool applies versus live presence lookup, but there is no explicit when-to-use, no pointer to ably_get_presence or ably_get_channel_history, and no note on prerequisites such as the presence capability or channel existence. Usage is only implied.
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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