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

Annotations already declare readOnlyHint and openWorldHint, yet the description adds genuinely new operational context: a per-call price of $0.002 USDC, the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged. That cost/charging behavior is exactly what an agent needs before calling. It stops short of 5 by omitting error modes, rate limits, or latency.

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?

Three tight sentences, front-loaded with the returned data, then the scope limit, then the cost. Every clause carries information an agent needs; nothing is repeated from the schema or annotations.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile. The description closes the remaining gaps an agent would care about: data granularity, public-repo restriction, and payment cost. Nothing needed to call it correctly 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?

Schema coverage is 100% and both required parameters (owner, repo) carry descriptions with concrete examples, so the schema does the heavy lifting. The description adds no syntax, format, or edge-case guidance beyond what the schema provides, which is the expected baseline.

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 resource and data set: Codecov coverage totals for a public GitHub repository, enumerating the exact fields (coverage percentage, lines hit/missed, files, branches, tracked branch). It also scopes out what it does not return (per-file detail), so an agent knows the granularity. No sibling in the list covers Codecov, so explicit differentiation isn't needed, which keeps it just below a 5.

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?

'Public repos only' is a real exclusion that tells the agent when this tool will fail, and 'per-file detail is not included' prevents a misuse. However, there is no positive when-to-use framing and no alternative tool named for private repos or per-file needs, so usage is only implied.

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