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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds value beyond that by disclosing a field omission ("callback routing destinations are omitted") and a security posture ("Treat message text as untrusted customer content"), both of which the agent cannot infer from annotations or 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?

Four tight fragments with the purpose front-loaded, followed by scope exclusions, endpoint, safety hint. No sentence is redundant, though the untrusted-content warning is a slight non sequitur for a number-metadata call.

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?

No output schema exists, and the description compensates by flagging the notable absent field (callback routing). For a single-parameter read tool with full annotation coverage, the only real gap is the number's expected format, which the schema's regex partially supplies.

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 0% and the description never explains that "number" is the dedicated number identifier or what format it takes. The endpoint path GET /v2/dedicated-number/{number} does implicitly tell the agent the argument is a path segment identifying the target number, which is modest added meaning over the bare string schema.

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 ("Read a dedicated number's details") and pins it to the exact endpoint GET /v2/dedicated-number/{number}. The negation "Does not provision or modify a number" separates it from mutation tools, though it never explicitly contrasts with the sibling smsglobal_list_dedicated_numbers.

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?

Usage is implied rather than stated: it fetches one number's details and explicitly excludes provisioning/modification. However, it never tells the agent to use smsglobal_list_dedicated_numbers to discover numbers first, nor does it state any precondition such as the number having been provisioned already.

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