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

With no annotations, the description carries the full burden. It details the return contents: 'total counts of mutations, genes, and unique mutant peptides, plus how many cell lines, tissues, and cancer types are covered, and the data sources.' This discloses the behavioral trait of returning aggregate statistics. It does not mention side effects, but the read-only nature is clear.

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 three sentences, front-loaded with the core function, then lists return values, and ends with usage guidance. Every sentence adds value without redundancy. It is appropriately sized for a simple tool.

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?

Even without an output schema, the description enumerates the return payload in detail (counts of mutations, genes, peptides, cell lines, tissues, cancer types, data sources). It also provides usage context and parameter information, making it a complete description for a zero-parameter tool.

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 tool takes no parameters, so the schema is empty. The description explicitly states 'No parameters,' reinforcing this. There is nothing else needed for parameter semantics, matching the baseline for zero-parameter tools.

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: 'Get the headline size of the CAN-IMMUNE database in one call.' This distinguishes it from sibling tools that lookup specific entries or list options. The verb 'Get' and resource 'database' make the function clear.

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?

Gives explicit usage context: 'Use this first to size the resource or to answer "how big is the database / how many X are there" questions.' This implies when to reach for this tool over others, though it does not explicitly name alternatives or exclusions.

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