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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly mentions idempotency ('return the existing one', 'idempotently'), the side effect of granting post/read access to current members, and the quota_exceeded error. This goes well beyond the schema and gives the agent a clear picture of what happens on call.

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?

The description is two sentences, front-loaded with the primary purpose and then detailing the alternative mode and a key error condition. There is no fluff; every clause contributes to the agent's understanding. The structure is logical and efficient, making it easy to parse quickly.

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?

The description covers the main behaviors: creation, idempotent return, group-specific opening, and quota limit. It implies the return value ('return the existing one') but does not explicitly state the output format or what happens if both name and group are provided. Given there is no output schema, a more explicit statement about the return value would improve completeness, but the core usage is sufficiently covered.

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 100%, so each parameter already has a description. The tool description adds value by clarifying that name and group are mutually exclusive ('with group instead of name'), and that group must be a group you own. It also reiterates the auth nuance for tenant_key. This enriches the schema without repeating it verbatim, though it does not add syntax-level details beyond what the schema provides.

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 clearly states the tool's core function: create or return a named channel, or open the one channel for a group you own. It uses specific verbs and resources, and distinguishes itself from sibling tools like host.channel.close or host.channel.freeze by focusing on creation/opening. The two modes (name vs group) are explicitly described, leaving no ambiguity about what the tool does.

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 description gives clear guidance on when to use this tool: when you need to create or open a channel, either by name or by group. It implies alternatives by naming other actions like post/read, but does not explicitly state when NOT to use it (e.g., for closing or freezing). However, the context is clear enough for an agent to infer the appropriate use case. It also mentions the quota_exceeded failure condition, adding practical usage guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.