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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real behavioral context beyond them: the call is free and spends nothing, and it explains the payer model (personal vs team, with team project runs always drawn from the team pool) plus the payer balance. That cost/payer semantics is not derivable from the annotations.

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?

Single dense sentence with the free/no-spend qualifier front-loaded and the actionable handoff to start_run at the end. Every clause carries information (cost, payer, balance, per-node price, version) with no filler.

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 takes on the burden of describing the return shape, and it does so (total, payer, payer balance, per-node price and model, canvas version). Combined with the explicit start_run chain, an agent has enough to call and use it, though the exact response structure is only named, not shaped.

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 four inputs (graph_id, force_nodes, scope_nodes, from_node_id) are already documented in the schema. The description instead elaborates on return fields and the start_run handoff, adding no meaning to the input parameters themselves; baseline 3 applies when the schema does the heavy lifting.

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 (price/estimate) on a specific resource (a canvas run) and immediately distinguishes it from write operations with '(free, spends nothing)'. The word 'canvas' plus the return-field list separates it from estimate_generation and estimate_upscale without opening either schema.

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?

Clearly positions this as the pre-flight check for start_run and names the handoff explicitly ('Pass the total and the version to start_run'). The workflow is unambiguous, though it gives no explicit exclusion such as when to prefer estimate_generation or what to do if the price is unacceptable.

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