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

With no annotations, the description carries the burden of behavioral disclosure. It adds a billing note ('Billing per call: 1 Credits'), which is useful context beyond the basic action. However, it does not disclose potential errors, limitations, or data source specifics, leaving some behavioral gaps.

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 sentence and relatively concise, combining purpose and billing info. However, it lacks proper punctuation (missing period before 'Billing') and mixes two ideas without clear separation, slightly reducing clarity but not significantly.

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 tool with no output schema, the description covers the main purpose and even mentions the output (associated name). However, it omits the meaning of 'code' and provides no usage context or edge-case behavior, leaving the tool somewhat incomplete for an agent to fully rely on.

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?

The schema has zero description coverage for the two parameters. The description explains that 'number' is a phone number, but it leaves 'code' completely undefined. This is a significant gap, as the agent cannot infer what 'code' represents, leading to potential misuse.

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 clearly states the tool's function: searching for contact information and identifying the name associated with a phone number. It uses a specific verb ('Searches') and resource ('contact information'), and distinguishes itself from the sibling tool (getCountryCode) by focusing on phone number to name lookup.

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 description implies usage: use when you need to identify a name from a phone number. However, it does not explicitly state when to use this tool versus the sibling getCountryCode, nor does it provide exclusions or alternative scenarios. Thus, only implied guidance.

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