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

Beyond the readOnly/idempotent annotations, it discloses several non-obvious traits: values are account-scoped and may change, route_revision signals when they changed, descriptor.price is a default/display value rather than a final price with media inputs, and effective_values are the true defaults. It also states a hard boundary ('Never request provider, routing, payer or billing internal fields from the user').

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 usage trigger is front-loaded in the first clause, and nearly every sentence carries distinct information (per-account variance, price caveat, effective defaults, aspect preservation). It is a single dense block mixing usage, return semantics, and behavioral rules without paragraph separation, which costs it a bit.

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 inspection tool with an output schema, the description covers the workflow position, account-scoping, and how to interpret descriptor.price and effective_values. The main omission is any explanation of the values/canvas_project_id parameters, which an agent will need when building a real call.

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 only 20% — only execution_model_key is documented in the schema — and the description never explains family, values (the overrides object), canvas_project_id, or lang. Terms like 'overrides' and 'effective_values' gesture at the domain but give no mapping to the input parameters, so it does not compensate for the coverage gap.

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 states a specific verb and resource ('returns authoritative public controls, effective_values, conditional media slots, input modes, overrides and info_text') scoped to a selected model family/version for THIS account. It clearly separates itself from the pricing siblings (aimixer_estimate, aimixer_quote), though it does not differentiate itself from discovery siblings such as aimixer_catalog or aimixer_model_card.

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?

Explicit trigger is given ('when an exact MixerAI model family/version is selected and before any estimate or paid quote') plus re-read guidance ('read them again before each quote'). It names the alternatives and their conditions ('use aimixer_estimate for price comparisons, and aimixer_quote only for a complete real generation'). It stops short of saying when NOT to call it versus the catalog/model_card discovery tools.

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