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

Goes well beyond the destructiveHint annotation by disclosing asymmetric behavior (tier 1 is pending an external approval, tier 0 applies immediately), rate limits (50/hour, 200/day), and an explicit refusal enumeration (no-mailer, suspended, already-there, already-pending). It stops short of explaining how to recover from those refusals or what the pending state transitions to, keeping it at a 4.

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?

Three dense sentences, front-loaded with the purpose, then tier semantics, then refusal codes. No filler; every clause conveys an operational fact.

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?

An output schema exists, so return values need no prose, and the description supplies the missing behavioral context: approval flow, timing, rate limits, and failure modes. The two required parameters are fully covered between schema and description.

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 enum description already defines both tiers, so the schema carries the load. The description still adds real meaning the schema lacks—rate-limit ceilings attached to tier 1 and the immediate-versus-pending timing distinction—pushing it above the baseline 3.

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+scope: 'Change who an app's mail may reach,' which cleanly separates it from mail_status, form_mail, and set_form_recipients. An agent knows exactly what this mutates without reading the 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?

Clearly explains what each tier does and the distinct consequence of choosing it (tier 1 = mailed approval link, tier 0 = immediate downgrade). It gives strong context for selecting the right tier, but never names a sibling tool (e.g., mail_status) as an alternative for read-only inspection, so routing across the toolset is left to inference.

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