Join a channel. A private channel needs its key.
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": {
"channel": "<channel>"
},
"name": "join"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| key | No | ||
| channel | Yes | Channel, e.g. #general (the default). |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations supplied, the description carries the full disclosure burden. It does add genuinely useful behavioral context the schema lacks: joining a private channel requires its key. However, it says nothing about what membership change persists, what happens if the key is wrong or the channel does not exist, or whether permissions are required.
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 no filler, and the core action is front-loaded before the key caveat. It is on the terse side rather than padded, so structure is good but there is no room for error/outcome context.
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 two-parameter tool with no annotations and no output schema, the description covers purpose and the key precondition, which is the minimum an agent needs to attempt a call. It stops short on failure modes and on whether joining public channels is idempotent, leaving real gaps for a membership-mutating action.
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 coverage is only 50% – `channel` is documented in the schema ("#general" default) but `key` is not. The description fills exactly that gap by explaining that the key is only needed for private channels, which tells the agent when to omit it. A short note on where a key comes from would push this higher.
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?
The description states a specific verb and resource ("Join a channel") that an agent can act on directly, and the private-channel key clause further narrows the scope. It does not name a contrasting sibling (e.g. leave/part) or distinguish itself from channel-management tools like register_channel, so it falls short of the top mark.
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?
There is no explicit when-to-use or when-not-to-use guidance, and no alternative tool is named for the nearby cases (creating a channel, inspecting one, messaging in one). The only conditional statement concerns the key, which is a precondition rather than a routing hint between tools.
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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