check_upgrade_eligibility

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

With no annotations, the description carries the full burden, but it only says 'Check' and does not disclose what the tool returns, whether it makes an external network call, whether authentication is required despite optional credentials, or whether any state changes occur.

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?

The description is a single front-loaded sentence with no filler. It immediately communicates the verb, target, and scope, making it easy to parse.

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 simple read-style tool with fully optional, documented parameters, the description is adequate but has gaps: no output schema and no mention of what the response looks like or what conditions might affect eligibility. It is serviceable but not rich enough for full autonomy in ambiguous situations.

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%, so the parameters are already well documented in the input schema. The description adds the context that eligibility applies to 'lines on the account,' but it does not add meaning beyond the schema's parameter descriptions.

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?

The description states a specific verb ('Check') and a clear resource ('T-Mobile device upgrade eligibility for lines on the account'). It is distinct from the sibling tools, which cover overview, usage, payments, and billing, though it does not explicitly contrast itself with them.

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 intended use case is implied by the description: call this when upgrade eligibility is needed. However, there is no explicit guidance about when not to use it, prerequisites for authentication, or how it relates to the sibling account tools.

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