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

Beyond the annotations (which already cover read-only/idempotent), the description discloses prerequisites an agent cannot infer: a Last Price credential is required, and a sandbox key from self-registration is refused with a 403 until a person claims the workspace. That authentication/eligibility failure mode is exactly the kind of context annotations don't carry.

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?

Front-loaded with the core purpose followed by filtering, paging, and then prerequisites in priority order; every clause carries information. It is dense with semicolon-packed sentences, and 'Read-only' repeats the annotation, but there is no real padding.

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 supplies the return shape (per-call purpose, provider, model, tokens, cost) and ordering, plus auth and workspace-claim requirements. An agent has everything needed to decide, call, page, and anticipate a 403.

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 100%, so all five parameters are already documented in the schema. The description restates the filters (operation, start_date/end_date, limit/offset) without adding format details, range behavior, or how the filters combine, so it adds little beyond the schema baseline of 3.

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 and resource (list individual model calls) and immediately anchors it to the sibling aggregate tool get_llm_usage, clarifying it returns the per-call detail rather than the rollup. Ordering (newest first) and the returned field set (operation, provider, model, tokens, cost) make the tool's role unmistakable.

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?

Explicitly frames the choice: use this for the individual calls behind get_llm_usage, implying get_llm_usage for aggregates. It doesn't state a hard when-not condition or mention other adjacent siblings like list_usage_events or get_usage_breakdown, so the routing guidance is clear but not exhaustive.

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