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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds a real behavioral constraint the annotation does not: the required 'channel-metadata' capability, plus the underlying REST endpoint. It stops short of describing pagination or result shape, keeping it out of 5 territory.

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 tight sentences: the core action first, then the auth prerequisite and endpoint. Nothing is wasted and nothing is buried.

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 list tool with complete schema docs and no output schema, the description plus annotations cover what an agent needs to call it. Minor gap: no hint about pagination or the shape of returned channel entries, though the 'by' enum partly implies this.

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%, with 'by', 'limit' and 'prefix' fully documented in the schema including defaults and bounds. The description adds no param-level detail beyond that, so the 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 (Enumerate) and resource (channels currently active in the app), and the REST mapping 'GET /channels' confirms it. It is clearly distinguishable from siblings like ably_get_channel_details (single channel) or ably_publish_message.

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?

Gives a prerequisite ('channel-metadata' capability) but no explicit when-to-use versus alternatives, and no guidance on when not to use it (e.g. for a single channel it points nowhere). The auth caveat is helpful context but 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.