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

Beyond the annotations (readOnly=false, idempotent=true, destructive=false), the description discloses the API-key requirement, the zero-credit cost, and the exact return JSON shape. That is meaningful operational context the agent would otherwise have to guess.

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?

Front-loaded with the primary action, then usage rules, then prerequisites and returns. Dense but every sentence carries actionable information; only the long field enumeration is slightly list-like.

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?

For a 7-parameter mutation tool, the description covers purpose, channel routing, auth requirement, cost, and return shape, with annotations already handling the safety profile. Nothing essential to correct invocation 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 description coverage is 100%, so the schema already documents every parameter. The description names the controlled fields but adds no syntax, format, or default behavior beyond what the schema provides, so it lands at the baseline of 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 and resource ('Configure per-app module switches ... plus sender brand name and Reply-To email address') and enumerates exactly which switches are controlled (OTP, webhook receipts, order status, push). An agent can distinguish it from siblings like send_transactional_email without opening 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?

Explicitly states the when ('enable or disable individual channels per website') and the when-not with a named alternative ('do not use it to send an immediate email or OTP (use send_transactional_email instead)'). The routing decision is fully specified.

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