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

Adds substantial behavior beyond the annotations: it reaches an external party (openWorldHint confirmed), requires an email address on file, needs an API key with app access, and by default confirms each call with the user. These are meaningful operational facts an agent needs before invoking.

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-loads the core action well, but the first and second sentences are redundant, both restating that an estimate is emailed to the customer with a link to approve online. The repetition costs space without adding information.

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 mutation tool with no output schema, it covers the essentials: external reach, email prerequisite, confirmation behavior, and auth requirement. Only the explicit return/result of sending is unspecified, which is a minor gap.

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 both parameters (estimate_id, message) are already documented in the schema. The description only echoes 'your optional note', adding no syntax or format detail beyond the schema, so 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?

States a specific verb and resource (email/send an estimate) plus the mechanism (link to approve online) and the audience (the customer). This clearly separates it from siblings like yardbook_create_estimate or yardbook_list_estimates, so an agent knows exactly what action it performs.

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?

Provides clear usage context: the estimate is a draft, the customer must have an email on file, and each call is confirmed by default. It does not explicitly name alternatives (e.g., 'use yardbook_create_estimate to build one first'), so it falls just short of full when/when-not guidance.

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