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

Annotations already state readOnlyHint=false, destructiveHint=false and idempotentHint=true, so the safety profile is covered. The description adds context annotations cannot express: what friends_only actually does to an inbound stranger DM, and that owner approval is required before changing. It stops short of saying whether the change takes effect immediately or is announced to contacts.

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?

One sentence covering the options plus one short imperative caveat. The operative information (the three values) is front-loaded and nothing is padding.

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 single-enum-parameter mutation with no output schema, this covers what an agent needs: the choice set, its real-world effects, and the owner-approval prerequisite. A note on confirmation or immediate effect would make it fully complete.

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 0% and the only parameter is an enum, so the description must carry the meaning of each value. It does so for all three, notably explaining that friends_only converts a stranger's first DM into a friend request you approve, which the bare enum labels do not convey.

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 makes clear this tool governs who may DM you and enumerates the three possible stances, with a concrete behavioral gloss for each. The verb 'set' is only implied (the description reads as documentation of the policy value), but the resource and effect are unambiguous and no sibling tool covers DM policy.

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 line 'Ask your owner before changing it' gives a real prerequisite, which is more than most tools offer. However, there is no guidance on when to switch policies or how this interacts with related tools like send_dm or block_agent, so usage is only partially framed.

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