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

The description adds behavioral context beyond the annotations: 'returned verbatim from the API' and 'unshaped rows' disclose that no transformations are applied. Annotations already cover read-only and idempotent hints, so the extra context is a bonus, though it doesn't detail edge cases like missing IDs.

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?

Two concise sentences front-load the core purpose and reference the sibling tool. Every clause earns its place with no redundancy or filler.

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 single-parameter read-only tool with a clear output schema and strong annotations, the description covers all essential context: the exact input, output nature, and usage conditions. Nothing critical 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?

The schema provides a minimal description ('molecule_chembl_id'), but the tool description enriches it by specifying 'exact molecule ChEMBL ID' and giving an example format. This clarifies that partial or fuzzy IDs are not acceptable, adding meaningful semantic detail beyond the schema.

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 returns raw ChEMBL mechanism records for a single exact molecule ChEMBL ID, using a specific verb ('returned') and resource. It distinguishes itself from the sibling tool chembl_mechanism by framing its scope (already have the ID) and output (unshaped rows).

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?

Explicitly states when to use this tool ('when you already hold the precise molecule ID and want the unshaped rows') and identifies an alternative, chembl_mechanism, for starting from a drug name. This is textbook usage guidance.

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