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

Annotations already establish readOnly/idempotent/non-destructive behavior, and the description adds useful operational context: quota cost ('Counts as one call against the backlinks quota') and the release-diff semantics. No contradiction with 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?

Two tightly written sentences place the core diff definition first, then use cases and the quota note. Every clause adds value and there is no 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?

The definition covers purpose, use cases, defaults, and quota in combination with a fully documented schema. The only notable omission is the exact return shape (counts vs. lists), but this does not prevent correct invocation.

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 each parameter, including defaults, is already documented. The description reinforces the from/to release comparison but does not need to compensate for any schema gaps, so the 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?

The description names a specific resource ('referring domains for a domain') and the exact operation ('diff — what was added or lost between two Common Crawl releases'). This clearly distinguishes it from siblings like crawlgraph_backlinks and crawlgraph_releases.

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 explicit use cases: catching link rot, spotting sudden spikes (PR coverage), and outreach campaign attribution. It does not name alternatives or state when not to use it, but the context is clear enough for an agent to route appropriately.

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