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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds real value beyond that by explaining how the account id is derived from the control token and citing the underlying Control API endpoint. It does not mention pagination or result limits, keeping it from a 5.

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?

Three compact sentences, front-loaded with the action and return fields, followed by only the two facts an agent actually needs (auth resolution and endpoint). No filler.

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 zero-required-param read tool with no output schema, the description supplies everything needed: what is listed, the fields returned, and how the account scope is resolved. Nothing material is missing.

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% and the single parameter is already documented as an override. The description adds the fallback behavior (token-resolved account, ABLY_ACCOUNT_ID env var), which gives the parameter meaning the schema alone does not.

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 (list all apps in the account) and even enumerates the returned fields (id, name, status, tls-only), so the agent knows exactly what it gets. It never names or contrasts a sibling tool, so it lands at 4 rather than 5.

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 note that the account id is auto-resolved from the control token when ABLY_ACCOUNT_ID is unset is useful invocation context, but there is no explicit when-to-use/when-not guidance and no routing to alternatives (e.g., ably_list_keys or ably_list_namespaces for other resources).

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