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

Annotations already declare non-readOnly, non-destructive, non-idempotent. The description adds real behavioral facts beyond them: won/lost stages are rejected, the deal is placed in the resolved stage's pipeline, pipeline_id must match that pipeline, and title/currency defaults. It stops short of describing the returned handle or side effects like stage counters.

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?

Extremely dense but front-loaded: the create action and its stage constraint come first, defaults last. No filler sentences, every clause carries a constraint or a default.

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 6-param write tool with no output schema and no schema descriptions, the definition covers defaults, eligibility rules, and cross-parameter consistency. Missing only the return value (deal id?) and any rate/permission notes, which are minor for this shape.

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 0% across 6 params, so the description carries the load and largely does: it explains stage_id resolution, the pipeline_id consistency constraint, and defaults for title ('New deal') and currency (USD). amount is never characterized (units, sign, optionality), which is the one remaining 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?

States a specific verb+resource ('Open a deal for a contact') and immediately scopes it to open stages, which distinguishes it from create_pipeline, create_contact, and the update_deal/move_deal siblings. An agent knows exactly what object is created without opening the 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?

Gives a concrete prerequisite ('resolve stage_id with list_stages') and an explicit refusal condition ('a won or lost stage is refused'), which routes the agent correctly. It does not compare against close siblings like update_deal or move_deal, but the create-vs-update distinction is implied by the verb.

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