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

Annotations declare readOnlyHint=false, destructiveHint=false, openWorldHint=false, so the write capability is already known. The description adds useful context that unlisted callers get a message taken, but it leaves a critical behavior unstated: whether passing `people` replaces the entire list or merges with existing entries — a meaningful distinction for a non-destructive-flagged write.

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-pair with the resource definition front-loaded and the invocation rule trailing. Every clause earns its place, though the semicolon-compressed phrasing is slightly terse and leaves the overwrite question ambiguous.

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 one-parameter tool with no output schema and no annotation-level ambiguity about safety, the description is close to sufficient. It still omits what a read returns (presumably a list of names) and whether setting overwrites, both of which an agent needs to act correctly on requests like adding one person.

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 0% at the top level, so the description does real work by explaining that `people` sets the allowlist and that omitting it triggers a read. However, it does not clarify replace-vs-append semantics or whether order matters, so meaning is only partially added beyond the nested name/note property descriptions.

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 resource — the list of people the agent puts straight through to your person's line — and contrasts it with the fallback behavior (everyone else gets a message taken). The verb is implicit (pass `people` to set, nothing to read), but the dual-mode get/set nature is clear and no sibling tool covers similar ground.

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 explicit invocation guidance covering both modes: pass `people` to set, pass nothing to read. It also explains the real-world consequence of list membership, which lets an agent judge whether the user's request pertains to this tool. No exclusion cases or prerequisites are mentioned, but no plausible alternative exists.

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