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

Beyond annotations (readOnly, idempotent, non-destructive), the description adds rich behavior: out-of-domain requests are rejected (never clamped), the response echoes inputs/spec version/assumptions/sentinels/constants, and outputs are untouched engine results. This gives the agent a clear understanding of validation and return behavior far beyond what annotations declare.

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 description is four sentences, each earning its place: purpose, input requirements, response contents, and share link. It is front-loaded with the primary action and contains no redundant or filler text.

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?

Even without an output schema, the description fully describes the response contents (echoes, spec version, assumptions, sentinels, sourced constants, untouched outputs). It also covers the critical input contract and provides usage context for scenario models. Combined with the rich schema and annotations, it gives a complete picture for correct invocation.

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 baseline is 3, but the description meaningfully elaborates on the 'inputs' parameter by specifying contract requirements, all fields required, and rejection rather than clamping. It also reiterates that the api_key is only needed for non-free models, though this is already in the schema; the added contract semantics justify a score above baseline.

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 clearly states the tool runs a Concordance-tested calculation model with a specific verb ('Run') and resource ('calculation model'). It differentiates from siblings like get_model_contract (which provides contracts) and list_models (which lists models), making its purpose unambiguous.

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?

The description explicitly references get_model_contract as a prerequisite, stating inputs must satisfy that contract, which tells the agent when to use this tool and what to do first. It also provides guidance for scenario models by suggesting sharing the interactive calculator link, though it does not explicitly mention when not to use the tool.

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