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

Annotations already establish readOnlyHint=true and the description confirms 'Read-only' without contradicting it. It adds genuine behavioral context beyond the annotation by decoding what the returned statuses mean ('sent_from_gmail' vs 'opened_in_gmail') and enumerating the note states (failed, waited too long, still waiting) plus the interaction types recorded.

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 core purpose and window are front-loaded before the enumerated details, the invocation triggers, and the read-only note. It is a dense, comma/semicolon-heavy run-on, but nearly every clause carries information an agent needs given the absence of an output schema.

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?

With no output schema, the description does real work by enumerating what comes back and what the status codes mean, which is sufficient for an agent to call it correctly. It omits result ordering, volume limits, and response shape, keeping it short of a 5.

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 `days` parameter is fully documented there (default 7, max 31). The description only restates the default, so the schema is doing the heavy lifting and the baseline of 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?

The description names a very specific retrospective scope: the briefs written, notes sent and how, notes sent unasked, failed/stale/pending notes, and every user response. 'What Your day did for the user' is a concrete verb+resource that is clearly distinct from planning/attention siblings like my_day or what_needs_attention.

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?

It gives explicit invocation triggers ('what did Your day send?', 'did anything go out for me?', 'what did I approve this week?'), which is strong when-to-use guidance. It does not, however, name the alternatives it should not be used for (e.g., my_day or what_needs_attention) or state exclusions, so it falls short of a 5.

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