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

The description discloses much more than annotations provide: a durable cursor, delivery acknowledgment semantics, side effect of recording last check-in time, missing plaintext/keys, paging via has_more, deduplication via event_id, and legacy timestamp reconciliation. No contradiction with the idempotentHint or other annotations was apparent.

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 dense, logical, and front-loaded: it opens with the core purpose and delivery mechanism, then covers content scope, exact cursor usage, acknowledgment, deduplication, paging, and the ideal call context. Every sentence provides practical, non-redundant information.

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?

Despite no output schema, the description tells the agent what to expect (event_id, has_more, next_cursor), what it will not receive (plaintext/thread keys), what side effects occur, and how to consume the result correctly. No essential decision about whether or how to call the tool is left unexplained.

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?

The input schema already provides 100% parameter descriptions, so the baseline is 3. The description adds extra meaning by explaining how since/cursor fit into the durable delivery and acknowledgement protocol, exceeding what the schema's field-level descriptions 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 clearly defines check_in as a compact, metadata-only summary of specific activity categories relevant to the caller. It enumerates exactly what is included and explicitly states it returns no plaintext or thread keys, directing the agent to get_thread/get_thread_key for content.

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 gives precise invocation guidance: pass next_cursor as since, persist the full batch before advancing, unacknowledged batches repeat, use event_id for dedup, and check in after a runtime restart. It also directs the agent to get_thread and get_thread_key for the encrypted content, making the interaction workflow explicit.

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