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

The readOnlyHint annotation already covers the safety profile, and the description adds real value on top: the full set of possible per-recipient statuses, the fact that parts and cost are returned, and the 'free' cost note. It still omits whether statuses are eventually consistent (i.e. whether polling is expected), which matters for a delivery-report tool.

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?

Two sentences, front-loaded with the operation and its return shape, followed by the underlying REST mapping. The status enumeration is dense but directly useful and nothing is padded.

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 carries the return-value burden and does so reasonably by listing statuses, parts, and cost. It falls short only on error/timeout behavior and whether a pending status should be re-polled after a delay.

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% and the single request_id parameter is fully documented in the schema itself. The description adds return-value context but no additional syntax, format, or constraint information beyond what the schema already provides, 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 and resource ('Read the delivery status of an SMS request') and enumerates the exact status values the caller should expect. It is cleanly distinguished from siblings like d7_get_balance, d7_get_sms_pricing, and d7_send_sms, which deal with pricing, balance, or sending rather than post-send delivery reporting.

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 makes the usage context clear (checking delivery of an already-submitted SMS request) and the schema ties request_id to d7_send_sms's return value, establishing the natural call order. It does not, however, state explicit exclusions or name an alternative tool for overlapping reporting needs such as d7_get_lookup_report.

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