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

readOnlyHint=true already tells the agent this is a safe non-mutating read, so the description only needs to add context. It adds the scope of returned data (type, flow, sender IDs, limits, consumption), which is useful given there is no output schema, but it says nothing about permissions, freshness, or not-found behavior.

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 compact sentences, with the payload summary front-loaded ahead of the endpoint literal. The endpoint string adds little for an agent but costs almost nothing.

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 single-parameter read tool with no output schema, the field enumeration plus the read-only annotation give an agent enough to call it and anticipate the response shape. Error and empty-result behavior remain unaddressed.

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 coverage is 100%: channel_id is documented with a UUID pattern and a hint to obtain it from smsmode_list_channels. The description's 'channels/{id}' merely restates the schema, adding no new syntax or constraint detail, so 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 ('Details of one channel') and enumerates the fields returned, so an agent knows this is the single-channel counterpart to smsmode_list_channels. It stops short of naming the sibling explicitly, so differentiation is implied rather than stated.

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 phrase 'one channel' implicitly tells the agent this is for a single known channel rather than a listing, but there is no explicit when-to-use, no exclusion, and no named alternative. Usage must be inferred from context.

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