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

readOnlyHint=true already establishes this as a safe read, so the burden is lower. The description goes beyond that by disclosing exactly what comes back (delivery status, delivery date, recipient network, text, parts, price), which is genuinely useful given there is no output schema.

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?

One tight sentence of return contents followed by the endpoint path; no filler and the resource is front-loaded. Nothing could be cut without losing information.

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 two-parameter read with no output schema, the enumerated return fields cover the main gap, and readOnlyHint covers safety. Error behavior (e.g. how a missing/invalid id is reported) is the only notable omission.

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 message_id and channel_id are fully documented in the schema, including where the id comes from. The description adds no parameter-level syntax or constraints, 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+resource (retrieving one message) and enumerates the returned fields, which distinguishes it from the plural smsmode_list_messages. It stops short of explicitly naming the sibling it is not, so it lands just under the top band.

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 no when-to-use guidance, no prerequisites, and no routing against smsmode_list_messages or smsmode_get_campaign. The '{id}' path implies a single-record fetch but nothing in the text tells the agent when this is the right call versus a list.

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