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

Annotations already declare readOnly, idempotent, and non-destructive behavior; the description adds non-obvious context: data comes from an in-memory ring buffer (recent/ephemeral), records include inputs/expression/result, and traces can be bulky. This clearly goes beyond what annotations provide, with no 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?

Three sentences with no waste: front-loaded purpose and return type, then a special-case path, then a practical advisory about bulk output. Every clause 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 read-only diagnostic tool with readOnly annotations, the description covers purpose, path syntax, constraint paths, data source, and limit handling. Although there is no output schema, the 'inputs, expression, result' hint gives the agent a sufficient model of the returned trace records.

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 adds meaning beyond the schema: 'path' accepts a synthetic '$constraint:<id>' form, and 'limit' is motivated by trace bulk. It doesn't add to 'id', but the schema already documents that clearly.

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?

States a specific verb ('Explain why a field is what it is') and the exact return artifact: recent derivation/constraint trace records for a path. This distinguishes it from siblings such as get_field (current value) or get_history (change history), and the synthetic path special case reinforces its exact scope.

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?

Gives explicit usage direction for constraint paths ('$constraint:<id>') and advises passing 'limit' when trace records are bulky. However, it names no alternatives or exclusions, so an agent must infer from sibling names when to prefer explain over get_field, get_history, or get_audit.

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