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

Annotations declare readOnlyHint=false and destructiveHint=false, and the description is consistent with that ('Create' = write, non-destructive). It adds value beyond annotations by disclosing the cost profile ('No charge') and the underlying API call, though it omits idempotency/dedup behavior for repeated address creation.

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, front-loaded sentences with no filler: capability, cost, and endpoint. Every clause earns its place.

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?

With no output schema, the description correctly takes on the return-value burden by naming deliverability and normalized/corrected fields. For a 10-parameter write tool it leaves the parameter story thin, but the core transactional picture (what it does, what it returns, what it costs) is complete.

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 only 40% across 10 parameters, so the description must compensate, and it largely does not. It hints at the API body shape ({ address, verify: ["delivery"] }) but never maps this to the actual input fields or explains the undocumented ones (name, email, phone, street2, company).

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 ('Create and verify a US or international address') plus the outcome ('returning deliverability and normalized/corrected fields'), which is far more informative than the bare title. It does not explicitly differentiate itself from siblings like easypost_get_address or easypost_list_addresses, though the 'verify' capability is implicitly unique in the set.

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 (verify before shipping) and the 'No charge' note gives an incentive to prefer this over other flows, but there is no explicit when-to-use statement, no exclusions, and no named alternative for address validation. The agent must infer context.

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