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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint=false), the description explains the actual behavior: it computes a price, returns an external billing link, never charges, and never handles payment data. This resolves the obvious ambiguity of a tool named 'start_plan_upgrade' that is nonetheless read-only, and explains where the transaction actually completes.

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 with zero padding: purpose and return value first, safety and payment-location caveat second, the Enterprise exception last. Every sentence carries distinct information an agent needs.

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?

There is no output schema, and the description compensates by stating the return value (a secure billing link). For a two-parameter, non-charging pricing tool, the description covers purpose, safety, payment location, and the Enterprise exception — nothing material 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 coverage is 100% with enums on both parameters, so the baseline would be 3. The description adds real meaning on top by noting the monthly-or-yearly dimension and, more importantly, that Enterprise selection is not self-serve but must go through Jobiba contact, which is not derivable from the enum alone.

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 opens with a specific verb and resource ('Prices an employer plan upgrade') and states what it returns (the secure jobiba.com billing link), which is far more than the tautological title 'Upgrade my plan'. It does not explicitly name a sibling such as get_membership_plans as the place to browse plans first, which keeps it from a 5.

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 frames the scope of use: pricing only, no charge, no payment details collected, payment completed on jobiba.com, and Enterprise routed to contacting Jobiba. The Enterprise caveat is genuinely actionable against the ENTERPRISE enum value. It stops short of telling the agent to call a plan-listing tool first, so no explicit alternatives are named.

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