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

Annotations already declare readOnly, idempotent, non-open-world, non-destructive, so the safety profile is covered structurally. The description adds genuine value beyond that: charged is false, no URL fetch/payment/receipt, and the important semantic that missing keys mean coverage-unknown rather than deletions. However, roughly half the text is repeated synthetic-example boilerplate rather than new behavioral disclosure, and it says nothing about the shape of the comparison result.

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 useful guidance occupies about three sentences; everything after that is a multi-kilobyte inline JSON example full of repeated 'SYNTHETIC offline construction example only' disclaimers. This bloats the definition and buries the operational rules, so the signal-to-noise ratio is poor even though the purpose is front-loaded.

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 is the only place a caller could learn what the comparison report looks like, and it never describes the return shape (per-field added/removed/changed, row matching, coverage-unknown flags). The input-side contract is thorough, but the output side is entirely 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 83%, so the baseline is 3, and the description goes past it by explaining the comparison contract: only explicitly selected data keys present on both matched rows, missing keys are coverage unknown, explicit null counts as a present value, unselected metadata is not a delta. That directly clarifies how 'fields' and the before/after payloads are interpreted.

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 opening sentence states a specific verb and resource: comparing two already-held extract-batch JSON artifacts. It also immediately rules out fetching or paying for a second observation. No siblings exist to differentiate from, so nothing further is needed on that axis.

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 gives clear when-not guidance ('Does not fetch, pay, or schedule a second observation'), implying use only when both artifacts are already in hand. It also defines comparison scope rules (selected keys only, both matched rows). It does not spell out an explicit trigger condition such as 'use this after two extract_batch runs', but the context is unambiguous.

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