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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds valuable context about the identifier system (Ensembl gene IDs) and the return fields (approved symbol, name, biotype, protein IDs, pathways, synonyms), which goes beyond the raw annotations without contradicting them.

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 compact yet information-dense. It front-loads example queries, then states the purpose, return fields, and use case in a single coherent statement. Every sentence earns its place with no fluff or redundancy.

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 an output schema, the description covers all essential aspects: what it does, what input it expects, what it returns, and when to use it. The presence of an output schema reduces the need to describe return values in detail, and the description already lists key return fields.

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 covers the single parameter 'ensembl_id' with a description and example, so baseline is 3. The description reinforces that Ensembl gene IDs are used as target identifiers, but this mostly restates the schema example. No additional parameter semantics beyond the schema are provided.

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: 'fetch a drug-target profile' for a given gene. It also provides concrete example queries ('Drug target profile for [gene]', 'is [gene] a druggable target') and distinguishes it from sibling tools like target_associations or target_known_drugs by focusing on the core profile.

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 clear usage context: 'Use for target characterization in drug discovery' and supports it with example query phrasings. It does not explicitly list exclusions or alternatives, but the context implies when this general profile tool is appropriate versus more specialized sibling tools.

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