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

The description adds a meaningful behavioral guarantee: credentials are never embedded in the comparison plan. This goes beyond the sparse annotations. It does not, however, disclose other behaviors such as whether the plan is persisted, validated, or immediately executed.

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?

Two efficient sentences fully front-load the purpose and add a relevant security constraint. There is no fluff or repetition of schema details.

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?

The tool has no output schema and minimal annotations, so the description should clarify expected return behavior and parameter semantics. It does neither in sufficient detail. The agent is left to infer what a 'plan' actually is and how custom model descriptors are interpreted.

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?

The schema has 0% description coverage, so the description must compensate. It only alludes to two parameter groups ('custom model descriptors' and 'built-in providers') but never explains prompt, uiLanguage, inputLanguage, outputLanguage, or the nested customModels fields. This is insufficient for a 6-parameter tool.

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 action ('Build a Compare Mode plan') and identifies the exact ingredients: built-in Poly-Glot providers and developer-supplied custom model descriptors. The 'custom' qualifier clearly distinguishes this from the sibling prepare_compare tool.

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 gives clear context: this is for building a compare plan involving custom model descriptors, as opposed to a standard compare. It also clarifies a timing aspect (credentials supplied only at execution time). However, it does not explicitly name alternatives or state when not to use this tool.

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