Mail Tips

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new context: it uses the existing Mail.Read scope with no extra permissions, and it enumerates the per-recipient tip categories returned. It doesn't mention rate limits or latency, which keeps it from a 5.

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 information-dense but front-loads the core purpose and endpoint, then usage, then parameters. It is longer than typical but nearly every clause earns its place; the enumerated tip types are slightly list-heavy.

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 carries the burden of explaining what comes back, and it does so thoroughly by enumerating the tip categories. Combined with permission scope, usage guidance, and parameter behavior, an agent has everything needed to call 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 description coverage is 100%, so both parameters (recipients, tipTypes) are already documented in the schema. The description restates that recipients accepts a comma-separated string or array and that tipTypes defaults to all, but adds no syntax or behavioral detail beyond the schema. 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 action (pre-send recipient validation), the resource (mail tips), and the underlying Graph endpoint POST /me/getMailTips. It distinguishes itself from send-email and draft by positioning itself as a pre-flight check, so an agent can tell it apart from siblings without opening schemas.

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?

Explicitly says to use it ahead of send-email or draft action=create to catch OOO replies or external-recipient warnings, and notes that those tools can invoke it automatically via checkRecipients: true. This is a clear when-to-use with named alternatives and the condition that selects them.

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