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

Annotations already declare read-only, idempotent, non-destructive and closed-world behavior, so the safety profile is covered. The description usefully adds that values are omitted and that space usage is reported, but says nothing about ordering, pagination, or behavior for a nonexistent namespace.

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?

A single compact sentence with the main action and scope front-loaded and no filler. The trailing 'and the space used' is slightly awkward but carries real information about the result.

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 two-parameter read tool with rich annotations and no output schema, the description tells the agent what comes back (keys and space used) and what does not (values). That is enough to call it correctly; only listing-order and empty-namespace behavior are unstated.

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 both parameters are already documented; the description only restates that prefix filtering is optional and that the operation is scoped to a namespace. It adds no format, case-sensitivity, or matching-rule detail beyond the schema.

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 keys ... in a namespace') and clarifies scope by noting values are excluded, which separates it from memory_get. It does not name the sibling explicitly, so an agent must infer that memory_get is the value-fetching counterpart.

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 phrase 'without values' implicitly signals that this is the metadata-only listing and that memory_get should be used when values are needed, and 'optionally by prefix' describes the filter case. No explicit when-to-use/when-not or named alternatives are given.

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