search_by_cas_number

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool searches for compounds, implying a read-only operation, but doesn't clarify aspects like whether it returns a single compound or multiple matches, error handling for invalid CAS numbers, rate limits, or authentication needs. For a search tool with zero annotation coverage, this is a significant gap in 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?

The description is a single, efficient sentence: 'Search for compounds by CAS Registry Number'. It's front-loaded with the core purpose, has zero wasted words, and is appropriately sized for a simple search tool. Every part of the sentence contributes essential information.

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?

Given the lack of annotations and output schema, the description is incomplete. It doesn't explain what the tool returns (e.g., compound details, a list, or an error for no matches), behavioral traits, or usage context relative to siblings. For a search tool in a complex chemical domain with many alternatives, more guidance is needed to help the agent use it correctly.

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 input schema has 100% description coverage, with the parameter 'cas_number' fully documented in the schema itself. The description adds no additional parameter information beyond what's in the schema. According to the rules, when schema_description_coverage is high (>80%), the baseline is 3 even with no param info in the description, which applies here.

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 purpose: 'Search for compounds by CAS Registry Number'. It specifies the verb ('search') and resource ('compounds'), and the CAS Registry Number provides a specific identifier type. However, it doesn't differentiate from sibling tools like 'search_by_inchi' or 'search_by_smiles' that also search compounds by different identifiers, so it doesn't reach the highest score.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools like 'search_by_inchi' or 'search_by_smiles' for other identifier types, or 'search_compounds' for broader searches. There's no context on prerequisites, limitations, or typical use cases, leaving the agent to infer usage from the name alone.

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