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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds valuable behavioral context: it 'turns the absence of evidence into a forensic finding rather than a gap to fill with invention' and mentions the output includes 'safe wording for the agent to use.' This goes beyond the annotation without contradicting it.

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 description is front-loaded with the primary action and outcome, then provides a concrete example and use cases. Every sentence earns its place; it is detailed but not bloated.

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?

Given the output schema exists, the description does not need to enumerate return fields, but it does anyway in the example. Combined with the annotations, schema descriptions for all 4 parameters, and clear workflow contexts, this description is fully sufficient for an agent to select and invoke the tool correctly.

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 100%, so the baseline is 3. The description adds a concrete example (![hex] #4A535C + 'cyanosis in a death chamber') and explains what each major parameter contributes (hex and proposed_claim) and the nature of the response. This is more than the schema provides alone.

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 specific verb-resource pairing: 'Given a hex value and a proposed claim about it, return whether the archive supports that claim...' This clearly distinguishes it from siblings like archive_search, archive_coverage_gap, and colour_forensics by framing it as an anti-hallucination endpoint that produces 'safe agent wording.'

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 explicitly states when to use: 'Essential for museum, documentary, editorial, legal, and forensic workflows.' It does not mention when not to use it or explicitly name alternatives, but the context and example make the intended use clear.

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