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

Annotations cover the safety profile (readOnly=false, destructive=false, idempotent=true, openWorld=false), but the description adds real behavioural context beyond them: the ask flag triggers a request sent to the creator, and two distinct failure states are disclosed. It does not clarify what happens without ask on a friend's alarm the person isn't on, leaving one behaviour gap.

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?

Dense but earns nearly every clause, and the primary purpose is front-loaded. There is mild redundancy: 'For an alarm someone else made, by its link or code' restates the opening sentence, and the phrasing is occasionally awkward ('A friends alarm the person is not on can't be joined').

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?

No output schema exists, and the description compensates by stating the return ('the alarm's name, creator and when it rings') along with preconditions and side effects. For a two-parameter, non-destructive action, an agent has everything needed to invoke it 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 coverage is 100%, so the baseline is 3, but the description adds meaning the schema lacks: the link parameter can carry an alarm link, the message it arrived in, or a code, and explicitly excludes referral codes. That sharpens the accepted input beyond the schema's 'link (lfg.gm/a/...), the message it came in, or its code'.

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 ('Joins someone else's alarm') plus the observable effect ('it rings on the person's phone too'). The clause 'a referral code is not an alarm' separates it from the sibling use_invite_code, so an agent can route correctly without opening either schema.

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 clear preconditions and exclusions: only an alarm someone else made, a friend's alarm the person isn't on 'can't be joined' unless ask is set, and an alarm that already rang its last time can't be joined. It routes away from referral codes but never names the alternative tool (use_invite_code) explicitly, so it falls just short of full when/when-not/alternatives guidance.

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