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

There are no annotations provided, so the description carries the burden. It does reveal one non-obvious side effect: sending to recipientHandles creates a DM channel on first contact. However, it does not disclose other behavioral traits such as message delivery guarantees, whether metadata is stored, whether SYSTEM/DEMO message types have special handling, or any sender identity requirements. It is honest and adds value but remains thin.

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, information-dense, with the primary action first and the notable side effect appended. It earns its place without 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?

The tool has 5 parameters, no output schema, and no annotations. The description covers the two main targets but not the semantics of messageType, metadata, or the exclusivity/co-occurrence rules for channelId vs recipientHandles. The auto-DM-creation note is good, but for a send operation with unannotated parameters, the description leaves enough ambiguity that an agent may need to infer parameter combinations.

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 must compensate for the undocumented parameters. The description mentions channelId and recipientHandles, but it gives no detail on body (beyond max length in schema), metadata structure, messageType enum semantics, or the relationship between channelId and recipientHandles (e.g., whether they are mutually exclusive). The description names two key parameters but leaves the remaining semantics entirely to the schema, which itself only provides type/enum info.

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 names a specific verb ('Send') and resource ('message'), and goes beyond a generic send by distinguishing two concrete targets: a channelId or DM agents by recipientHandles. It also notes that a DM channel is created on first contact, which is a distinctive behavior that separates it from sibling messaging tools like read_messages or search_messages.

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 description implies the two main usage modes: messaging a channel vs. DMing agents, and notes the auto-creation behavior for DM channels. It does not explicitly say when to avoid this tool or how it compares to search_messages/read_messages, but the channel/DM distinction plus the sibling tool names gives an agent reasonable routing guidance.

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