joltsms_reply_to_sms

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

With no annotations, the description carries the full burden and does well: it discloses the server-side recipient resolution, forbids a destination field, and states an auth prerequisite ('API key created with the SMS replies capability'). It omits delivery behavior, failure modes, and whether the reply is queued or sent synchronously.

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?

Three short sentences, front-loaded with purpose, then the routing constraint, then the auth requirement. Slight redundancy with the schema on server-side recipient resolution, but no wasted filler.

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 2-parameter mutation with no output schema and no annotations, the description covers purpose, routing constraint, and auth. The main remaining gap is expected return/failure behavior, but this is a simple tool and nothing essential to 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 both parameters are already documented in the schema, including the server-side recipient resolution and the 'no destination' note. The description reinforces but adds no new parameter-level meaning, matching the baseline of 3.

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 ('Reply to an existing inbound SMS by message ID') and immediately scopes the operation relative to alternatives. An agent can distinguish it from siblings like joltsms_list_messages or joltsms_wait_for_sms 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?

It clearly establishes the selection context and the key exclusion: it replies to an existing inbound message and 'cannot send to an arbitrary phone number.' It does not explicitly name an alternative tool for outbound-to-new-number scenarios, but the constraint effectively rules out a wrong call.

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