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

Annotations already declare readOnlyHint=true, so the bar is lower. The description adds useful behavioral context: it detects whether primary_source date falls outside the period, flags known modern archives (RacingSilks, FootballStrips), and returns specific fields (risk level, period_relevance, safe/unsafe phrasing). This goes beyond the annotation without 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?

The description is composed of four purposeful sentences covering definition, detection logic, a use-case example, and output fields. No wasted words, though it is a bit longer than strictly necessary.

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?

With an output schema and read-only annotation present, the description adequately explains the tool's role and return values. It could be more explicit about expecting entries to contain archive and primary_source fields, but that is inferable from the schema.

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 covers 100% of parameters, so baseline is 3. The description adds semantic value by explaining that 'archive' values like 'RacingSilks' are known modern sources and linking 'primary_source' to date checking, giving meaning beyond the schema's bare descriptions.

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 states a specific verb ('check') and resource ('colour entries') and defines the exact risk detection criteria (source date vs period, known modern archives). It clearly distinguishes from sibling tools like archive_coverage_gap or colour_cultural_risk by focusing on anachronism, with a concrete example.

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?

The description provides clear usage context: 'Essential for historical documents' and a tangible example of a 2011 racing silk being misdated as Georgian. However, it does not explicitly mention alternatives or when NOT to use the tool, which would elevate it to a 5.

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