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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive open-world write. The description adds what annotations cannot: the required 'opportunities.write' scope and the pipeline/step dependency chain that must be resolved first. It does not mention duplicate handling or failure behavior, keeping it out of the top band.

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?

Three short sentences with the write classification and core requirement front-loaded, then the lookup pointers, then the permission. No filler or repetition of schema content.

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 an 11-parameter write tool with no output schema, the description covers the non-obvious essentials: the two required lookup ids, the related-record requirement, and the auth scope. It omits return-value expectations and optional-field guidance, but those gaps are moderate given the schema's 64% coverage.

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 64%, so the description must carry some weight, and it does: it establishes the cross-field constraint that the step id must belong to the given pipeline, which the schema lists as independent integers. It does not cover the optional fields (amount, probability, owner_id, assigned_staff_ids), but those are described adequately in the schema.

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 and resource ('WRITE: create a sales opportunity') plus its linking scope ('linked to a company, individual or contact'), which cleanly distinguishes it from sibling create_* tools that target other resources. An agent can tell immediately what this tool produces.

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?

Explicitly names the prerequisite lookups ('see sellsy_list_opportunity_pipelines and sellsy_list_pipeline_steps') and the required permission scope, so the agent knows the setup path before calling. It stops short of stating when not to use it (e.g., to update an existing opportunity, use the update counterpart), so it is clear context without exclusions.

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