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

The annotations already provide the safety profile (non-read-only, non-destructive, idempotent), so the description only needs to add unique behavioral context. It discloses a useful failure mode: sending a sprite while a custom icon image is set returns an error. This is valuable beyond both the annotations and the schema.

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 body is two sentences with the action front-loaded and the edge-case warning placed after. The repeated 'Update Source' heading is slightly redundant, but the overall description is lean and readable.

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 five-parameter mutation with a full output schema and annotations, the description covers the operation and a key error condition without restating schema details. It could add explicit partial-update semantics or permission requirements, but those are not critical given the schema coverage and annotation support.

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 the schema already documents id, name, slug, color, and sprite formats, constraints, and clearing behavior. The description's field list mirrors the schema but does not add meaningful parameter-level semantics beyond the error condition, which is more of a behavioral warning.

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 uses a clear verb–resource pair ('Update ... review source') and names the exact mutable fields: display name, slug, color, and sprite class. It does not explicitly contrast with createSource or updateReviewSource, but the field list and the word 'existing' make the tool's scope identifiable.

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?

It provides clear context by saying this is for an existing review source, which signals an update rather than a create or delete operation. It does not name alternative tools or explicitly state when not to use it, so it stops short of full routing guidance.

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