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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so no contradiction. The description adds valuable context beyond annotations by naming the data source (RFC 9110/IANA) and detailing what the lookup returns (canonical name, scenarios, mistakes). No missing safety caveats are needed because the tool is read-only.

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 two sentences long, front-loaded with the primary purpose in the first sentence. It immediately states what the tool does, gives search examples, and lists return fields without any filler. Every sentence 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 simple lookup tool with one parameter and an output schema, the description is complete. It covers purpose, search syntax, data source, and return content. No critical information is missing, and the output schema handles formal return-value definitions.

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?

The input schema has 100% coverage with a very detailed description of the 'query' parameter, including example values and behavior. The tool description's search examples ('404', '4xx', 'not found') merely echo the schema's parameter description, adding no extra meaning beyond what the schema already provides. Baseline of 3 is appropriate due to high schema coverage.

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 clearly states the tool's function: 'Look up HTTP response status codes from RFC 9110 and the IANA registry.' It uses a specific verb ('look up') and resource, and further distinguishes itself by explaining search modes (code, category, free-text). This is a distinct lookup tool among the sibling calculators/generators, so it scores high.

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 examples of when to use the tool ('Search by code (404), category (4xx), or free-text (not found)') which implies usage contexts like debugging. However, it does not explicitly mention when not to use it or name alternative tools. There are no exclusions, but explicit alternatives are missing, so it stays at 4 per the rubric.

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