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

Annotations already flag destructiveHint=true and readOnlyHint=false, but the description adds the critical detail the annotations cannot convey: the first call does not send, it only returns a preview plus a confirmToken, and the send only happens on the second call. It also discloses the inbox-plan requirement. This is exactly the behavioral context an agent needs to avoid an accidental irreversible send.

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?

Two sentences, zero filler, and the core action plus the two-step safety protocol are front-loaded. The SAFETY marker makes the non-obvious requirement scannable.

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 destructive mutation with no output schema, the description covers the key return value (preview + confirmToken) and the auth/plan prerequisite. It could go slightly further by stating that a confirmed send is irreversible and cannot be undone.

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 only 33% (confirmToken documented, id and text not). The description partially compensates by explaining the required confirmToken echo and that id/text must be identical across both calls, but it says nothing about the id format or the 1000-character text limit.

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 ('Send a DM reply in a conversation'), which is clearly distinct from the broadcast siblings (create_broadcast, send_broadcast) and from list_conversations. It does not explicitly name an alternative, so it falls short of a 5.

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?

Gives precise invocation guidance: call once with {id, text} for a preview, then call again with the same id, text, AND confirmToken to actually send. It also states the plan prerequisite. No explicit when-not or named alternative, but the procedural context is unusually clear.

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