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

Annotations already declare readOnlyHint=true, but the description adds genuinely useful context beyond that: 'Non-mutating (no mail sent)' clarifies this is a pure verification with no side effects, and the underlying endpoint (POST /v1/intl_verifications) is disclosed. It doesn't cover rate limits or response behavior, but the safety profile is well conveyed.

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, zero filler, with the scope constraint front-loaded and the API endpoint kept as trailing detail. 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?

For a simple verification tool with no output schema, the description covers scope, the required key parameter, and the safety profile. It could say more about what standardization returns, but nothing needed to invoke it correctly 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 only 50%, and the description only restates what the schema already documents for country ('2-letter ISO code, required'). It adds no meaning for primary_line, city, state, postal_code, or secondary_line, so it does not compensate for the coverage gap.

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 (validate & standardize an address) and immediately scopes it to non-US, which distinguishes it from the sibling lob_verify_us_address without the agent needing to open either schema.

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 'non-US' constraint and the required country parameter implicitly route the agent to this tool over lob_verify_us_address, and the note that no mail is sent clarifies the use case. It never names the US sibling explicitly, so the routing is inferred rather than stated.

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