List Retained Messages

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds valuable domain context about retained messages as 'last known value' and the risk of stale entries causing ghost entities. This helps interpret results but does not disclose pagination behavior or return completeness beyond the schema.

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 short and front-loaded with the core concept, but the first sentence is a grammatically awkward fragment ('Retained messages the broker is holding.') and the ghost entity warning, while useful, is a bit tangential.

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 simple list tool with full annotations and an output schema, the description adequately explains what retained messages are and a key pitfall. It could explicitly state that it lists all retained messages with pagination, but the title and schema already imply 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?

The input schema has 100% description coverage for both page and limit, so the description adds no extra parameter semantics. Baseline of 3 is appropriate.

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 identifies the resource (retained messages) and the context (broker holding them), making the listing purpose clear. However, the opening is a noun phrase rather than an explicit verb phrase, and it does not differentiate from sibling tools like emqx_get_retained or emqx_delete_retained.

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?

No explicit guidance on when to use this tool versus alternatives. The mention of ghost entities implies a use case (checking stale retained messages) but does not state when to choose this over emqx_get_retained or emqx_list_topics.

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