Routing Decision

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

Annotations only declare readOnlyHint=true; the description goes well beyond by enumerating the specific side effects that will NOT occur ('no model calls, callbacks, audit-file writes or approval execution') and adds a runtime dependency ('agenticlens>=0.10.0'). It also previews the return payload, giving the agent a full behavioral picture.

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, each earning its place: purpose first, return contents second, safety/dependency last. No filler or redundancy.

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 no output schema, the description correctly carries the return-value burden and covers the read-only profile and version requirement. The remaining gap is minor: it doesn't clarify where the 'saved ModelFit report' originates (presumably a sibling) or what session_id's shared state is used for.

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 description coverage is 75%, so the top-level params (policy, report, session_id) are largely documented in the schema itself. The description echoes the report/policy inputs but adds no format, precedence, or semantics for them, and the nested request properties (request_id, category_id) are undocumented in both places.

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') and resource ('a model route'), scoped to inputs from a saved ModelFit report and routing policy. This is clearly distinguishable from the closest sibling, lens.modelfit_recommend, which recommends rather than explains an existing route.

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 implies the use context ('from a saved ModelFit report and routing policy'), so an agent can infer this is for inspecting a route already produced. But it names no explicit when-to-use conditions, no exclusions, and no alternative sibling to prefer in other situations.

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