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

Beyond the schema and annotations, the description discloses that the bot/user must share a guild and that user_ids enables batched execution. These are meaningful operational constraints. It does not detail edge cases like duplicate sends, DM-disabled users, or account selection, which keeps it from being 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?

The description is compact, front-loaded with the primary action, and contains no filler. The prerequisite and bulk-support note are both directly relevant; every sentence earns its place.

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 tool with 5 parameters, no parameter docs, and no output schema, this description supplies enough for basic use: what it does, a key prerequisite, and batch mode. However, it omits clarification of account selection, message-only/embed-only behavior, the interaction of user_id and user_ids, and post-send expectations/errors.

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%, so the description needed to explain all parameters but only clarifies user_ids as the batch option. The required user_id is inferable from the name and 'DM with a user', but content, embeds, and account receive no semantic explanation, and the relationship between user_id and user_ids is left unclear.

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 clearly states the tool's action ('Open a DM channel with a user and send them a message') and specifies the target resource (a user DM). It also distinguishes itself from the sibling discord_send_message by emphasizing DM context, and it mentions the important guild-sharing prerequisite.

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 text gives useful usage context: it should be used for direct-message sending, only when the bot and user share a guild, and it supports batch execution via user_ids. It does not explicitly name alternative tools or say 'when not to use this,' so it stops short of a 5.

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