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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered and the description doesn't contradict them. It adds real behavioral value by disclosing the return contents and the fact that this is a single-record lookup keyed by slug. It stops short of error behavior (unknown slug) or whether results are cached/live.

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 sentences, front-loaded with the verb and cardinality, followed by the return summary. Every clause carries information an agent needs; nothing is restated from the name or title.

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 one-parameter read tool with no output schema, the description covers the essentials: what it fetches, the key format, and what the response contains. The only gap is the absence of any note on failure when a slug doesn't exist, which matters for a slug-keyed lookup.

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, but the description goes beyond it with a concrete literal example ("dual-3090-ryzen-3700x") that pins down the expected slug format. Combined with the schema's note that the slug is derived from a /builds/.../ URL, the agent has both provenance and shape.

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?

"Fetch one RigBase build by slug" names a specific verb (fetch), resource (RigBase build), and cardinality (one), which cleanly separates it from the sibling search_builds. The second sentence enumerates the payload (parts, measured results, source credit, canonical URL), so the agent knows exactly what it gets back.

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: the description says a slug is required and the schema says the slug comes from a /builds/.../ URL, which tells the agent the precondition but not the routing rule. It never names search_builds or best_gpu_for_model as the alternative for discovery workflows, so an agent must infer that this is the follow-up call after a search.

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