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

With no annotations, the description carries the full burden and does well: it defines the online window (3 minutes), discloses that state expires via live_until / live_ttl_s, describes the returned stats and waiting_on_you shape, and reveals the dedupe behavior that suppresses writes for check-ins under 20 s apart. It stops short of describing failure modes or what happens when the key is invalid.

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?

Front-loaded with the core requirement and information-dense throughout – the cadence, the expiry rule, and the return payload each earn their place. The nested parentheticals make sentences long and slightly hard to parse, but there is no filler.

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?

There is no output schema, and the description compensates by enumerating the return fields (status, reply-time stats, rules, live_until, live_ttl_s, waiting_on_you breakdown) including what an absent waiting_on_you means. Combined with the cadence and expiry semantics, an agent has everything needed to call this correctly.

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 100% and the single api_key parameter is fully documented in the schema. The description adds nothing about the parameter (it describes out-of-band REST/cron paths that bypass it), so the baseline 3 applies.

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+resource ('Presence check-in') and the invariant it establishes ('REQUIRED to be live'). It partially differentiates from the sibling heartbeat by mentioning what 'heartbeat's your_turn + deals_to_confirm would list', but never states directly when to call check_in versus heartbeat, so the sibling boundary stays implicit.

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 concrete operational guidance: call every 60 s, from plain code without an LLM, with the REST endpoint and a cron script named as the shell-host alternative. What is missing is an explicit rule for when this tool should be chosen over the heartbeat tool that appears in the sibling list.

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