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

Annotations already declare readOnlyHint=true, destructiveHint=false and a closed world, so the safety profile is covered. The description adds a genuine behavioral constraint not present in any structured field: the table must have history enabled for this to work. It stops short of 5 by not covering permissions or output shape.

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?

One tight sentence with the core behavior front-loaded, followed by an illustrative example and a prerequisite. No filler; every clause earns its place.

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 read-only comparison tool with no output schema, the description conveys what is returned (field-level differences) and the key precondition. The main gap is that neither the return format nor the identity/type expectations for 'table' and 'record_id' are elaborated.

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 50%: 'from' and 'to' are documented in the schema, while 'table' and 'record_id' are not. The description usefully clarifies the time semantics ('between an earlier time and now (or between two times)'), confirming that 'to' defaults to now, but does not compensate for the undocumented table/record_id parameters.

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: computing how a record's fields differ across time, with a concrete example ('what changed on job 42 since Monday?'). It does not explicitly distinguish itself from the sibling record_history, which likely covers overlapping ground, so it stops short of 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?

Provides a clear when-to-use scenario via the example question and states a real prerequisite ('The table must have history switched on'). It does not name an alternative tool or an exclusion, so it is clear context without explicit routing.

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