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

Annotations already carry readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is pre-declared. The description adds beyond that: preview mode, zero message delivery, no state changes, and informative output ('names the exact rule and how to remediate'). This aligns with the annotations and adds cost/de-risking context. No contradiction.

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?

The key facts are front-loaded (free, instant, pre-flight, same gate, no side effects), but the description carries rhetorical filler like 'de-risk' and the 'SAME... gate' emphasis, and it trails off awkwardly ('...the same way check_booking_link… [free, no key]'), which reads as a truncated thought. It earns a middle score: dense but not clean.

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 6-parameter tool with no output schema, the description covers the essentials: what it evaluates, in what mode, the safety profile, when to invoke it, and what the answer tells you (permitted, or exact rule + remediation). A fully explicit return structure or error-case discussion is absent, but the schema and annotations already carry the parameter and safety burden, so nothing critical 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 all six parameters in detail, meriting the baseline 3. The description adds only marginal framing by grouping the parameters into the send tuple '(recipient, channel, message_type, content)', which reinforces but does not materially extend the schema's per-parameter explanations.

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 states a specific function ('pre-flight for the compliance gate') and a specific resource: the TCPA/GDPR/CASL/CAN-SPAM/10DLC gate also used by send_message and call_business. It explicitly contrasts preview mode with real sends ('NO message is sent'), and tells an agent exactly what question it answers ('whether a (recipient, channel, message_type, content) send would be permitted'). This distinguishes it clearly from siblings.

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?

The description gives clear when-to-use context: 'de-risk a paid send' and 'BEFORE you pay for it', plus the free/no-key appeal. It contrasts with the actual-send tools (send_message, call_business) and alludes to a same-pattern sibling (check_booking_link), though that reference is truncated mid-sentence. It does not enumerate exclusions versus the sanction/restriction siblings, but the preview-vs-execute distinction is the load-bearing guidance.

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