Get contact

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

Annotations already indicate read-only, idempotent, non-destructive behavior. The description adds useful context beyond that: monetary values are integers in cents and the default field behavior. However, it contradicts the schema's claim that omitting 'fields' gives a compact default set, which slightly undermines transparency.

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 concise sentences, front-loaded with the primary action. Each sentence earns its place: the first states purpose and default behavior, the second gives an alternative usage path, and the third provides parameter narrowing and a unit caveat. No wasted words.

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 get-by-ID operation, the description covers main usage, alternative, field narrowing, and the key monetary unit detail. The schema richly documents the parameters. Gaps include missing an explicit note that customer_id is required and the fields default contradiction, but overall it is adequate for a tool with this complexity.

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 100%, so the baseline is 3. The description adds some value by noting the cents convention and explicitly saying to pass 'fields' to narrow the response, but it also conflicts with the schema's field default description. It does not significantly extend the parameter semantics beyond what the schema already provides.

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 'Fetch one contact by its numeric easybill ID', a specific verb+resource+identifier that clearly distinguishes this from list tools. The explicit pointer to easybill_list_contacts for name/number lookup reinforces the single-item retrieval purpose.

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 explicitly names easybill_list_contacts as the alternative when only a name or number is known, implying use this tool when you have the numeric ID. It also provides guidance on narrowing response fields, which helps the agent choose the right invocation.

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