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

Goes well beyond the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false) by disclosing a non-obvious side effect (resending restarts the automatic reminder cadence), channel prerequisites, that each call is confirmed by default, and the API key/scope requirement.

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 action and is appropriately sized, but the first two sentences overlap ('by email or text with a message' vs 'by email, text or both, with a custom subject and message'), which is minor redundancy rather than pure conciseness.

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 still covers prerequisites, side effects, and confirmation behavior adequately for a send action. It could be slightly more complete about delivery/response semantics, but nothing critical for 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 to/message/subject/channels/invoice_id. The description largely restates those fields rather than adding new syntax or format detail, so the 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 verb (send/resend) and resource (invoice) plus the delivery channels and target recipients, so an agent immediately understands the action. It is clearly distinguishable from housecall-pro_get_invoice and list_invoices without opening any 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?

Gives clear operating context (text requires online payments enabled on the invoice and a Mobile number; resending restarts reminders) and an explicit confirmation expectation. It does not, however, name a sibling alternative or state when NOT to use it, so it stops short of full when/when-not routing.

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