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

Adds substantial behavior beyond annotations: it sends even when the daily email is turned off, it queues asynchronously and returns immediately, and the agent should phrase delivery as 'on its way'. The async/side-effect profile is exactly what annotations (readOnlyHint=false, destructiveHint=true) cannot express. It stops short of saying anything about failure modes or what the return payload looks like.

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?

Opens with the action and scope, then triggers, then behavioral caveats, then parameter guidance – all in four dense sentences with 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?

No output schema exists, and the description compensates by explaining that the call returns after queueing and the email lands a minute or two later. For a one-optional-param send tool, nothing needed to call it correctly is missing.

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% and the single param is documented, so the schema carries the load; the description nonetheless adds conditional usage ('only when they name a topic to lead with') that the schema does not 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?

States a specific verb+resource ('Write the user's Daily Briefing now and email it') and scopes the content ('what is new since the last briefing they were sent'), which distinguishes it from neighbors like my_day, start_your_day, and send_email.

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 literal trigger phrases ('send me my daily briefing', 'brief me', 'email me my briefing') plus a parameter-level condition ('Pass focus only when they name a topic to lead with'), leaving little to inference.

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