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

Goes well beyond the annotations, which already declare openWorld, idempotent, and destructive. The description adds non-obvious behavioral facts: the action contacts the customer, requires business admin auth, blocks pending/unknown writes, and warns that provider acceptance does not prove customer delivery. These are exactly the operational caveats annotations cannot express.

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 verb+resource, then progressively narrower constraints (auth, idempotency, delivery caveat, attachment limit). Five short sentences with zero filler; each one adds a distinct fact an agent needs.

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 not be explained. The description covers purpose, authorization, idempotency/retry semantics, side effects, and the attachment limitation — everything an agent needs before invoking a customer-contacting write.

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 0%, so the description carries the burden. It adds real meaning for idempotency_key (must be stable, reused verbatim on retry) but says nothing about lead_id, business_id, or message beyond their names and schema constraints. Partial compensation for a 4-param, fully-required schema.

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") plus the exact resource and channel ("authorized text reply inside an existing Google LSA message lead through the Ads API"). This clearly separates it from siblings such as send_sms, send_message, and list_lsa_leads, and the qualifier "authorized" plus "existing ... lead" scopes exactly which replies qualify.

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 concrete preconditions (current business admin role, an existing LSA lead) and retry guidance ("Retry with the SAME key") plus a hard limitation ("Attachments are unsupported"). It does not explicitly name the alternative tools (e.g., send_sms/send_message) or say when NOT to use it, so it falls just short of full routing guidance.

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