send-serial-email

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

With no annotations, the description carries full burden. It discloses that emails are sent immediately, cannot be unsent, require explicit user confirmation, and that recipients do not see each other. It also states the return value (per-recipient report), exceeding what annotations would provide.

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?

Four short, front-loaded sentences organized logically (Use when, Returns, Do not use, Safety). Every sentence adds critical information with no waste.

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?

Given an output schema and 100% parameter coverage, the description covers selection, exclusions, safety, and return behavior. It is fully sufficient for an agent to decide when and how to invoke this tool.

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 parameters are already well-documented. The description adds context about placeholder replacement and per-recipient variables, but does not deeply elaborate on each parameter beyond what the schema already says. Baseline 3 is appropriate.

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 uses a specific verb ('sending individually personalized copies') and clearly identifies the resource (mail-merge to many recipients with placeholder substitution). It also distinguishes itself from siblings by naming send-email and create-draft as alternatives.

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 provides explicit when-to-use conditions ('user has confirmed a mail-merge', max 100 recipients) and explicit when-not-to-use with named alternatives ('use send-email', 'use create-draft'). This is clear, actionable guidance.

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