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

The description discloses behavior the annotations don't: the payload composition (classification into NEW_EVENT vs NEWLY_OBSERVED_HISTORICAL, materiality scoring with an attached rubric, duplicate folding) and the idempotent delivery guarantee. This is meaningful beyond the readOnly/openWorld/idempotent hints. Minor tension: readOnlyHint=false while the text reads like a retrieval, but there is no direct contradiction.

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 packed sentences, front-loaded with the deliverable and closed with the idempotency rule. Dense but no filler sentences; a little more air around the sentence 2 mechanics would help.

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?

There is no output schema, so the description carries the burden of explaining return content, and it does so by enumerating the change fields and the checkpoint handoff. It is complete enough to call correctly, though it stops short of the pagination/dedup edge cases and how to chain checkpoints over time.

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 watch_id, checkpoint, and include_historical fully; baseline 3 applies. The description reinforces the checkpoint round-trip ('Returns the next checkpoint') but adds no syntax or format detail beyond what the schema supplies.

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 ('material changes since a checkpoint') and enumerates what each change carries (filing, filing date, classification, materiality score), so the agent knows exactly what it gets back. The gap is sibling differentiation: it never distinguishes itself from the nearby 'changes_since' tool, which an agent will have to disambiguate unaided.

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?

Usage is only implied through the checkpoint mechanic ('Returns the next checkpoint; a repeated call returns the same delivery') and the schema's 'omit for the latest'. There is no explicit when-to-use statement, no exclusions, and no pointer to alternatives such as changes_since or watch_reevaluate.

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