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

Beyond the supplied readOnlyHint/openWorldHint, it discloses the commercial model: $0.002 in USDC per successful call via x402 across Base, Solana or Arc, with failed calls not charged. That is exactly the auth/cost context an agent needs before invoking a paid tool, and it does not contradict the annotations.

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?

Front-loaded with purpose, then lookup modes, then returns, then price — a sensible ordering. The return-field list is lengthy and partly redundant with the output schema, costing a point, but no sentence is 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?

Covers source authority (SIB Cellosaurus), all four input routes, the disease-search limit behavior, payment mechanics, and the charge-on-success rule. With an output schema present, the extra return-field enumeration is redundant rather than missing, so nothing an agent needs is absent.

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?

Schema description coverage is 100%, so every parameter is already documented with its own example (MCF-7, ACH-000019, CVCL_0031, 1–50 limit for disease search). The description restates the same input modes without adding syntax, precedence rules, or behavior when multiple identifiers are supplied — baseline 3 applies.

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?

States a specific verb+resource: look up a cancer cell line with DepMap IDs sourced from Cellosaurus, and also lists DepMap lines for a disease. No sibling tool in the list covers cell lines, so the resource is unambiguous by itself.

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?

Enumerates the four selection modes with concrete examples (name such as MCF-7, accession CVCL_…, DepMap ID ACH-…, or disease listing), which tells the agent exactly how to route a query. It does not state when to prefer this over a non-existent alternative or what happens with ambiguous names, so it stops short of a 5.

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