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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the 'WRITE:' label mostly repeats structured data. The description adds nothing about permissions/auth, duplicate-name handling, or what side effects a creation has on the customer record.

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?

A single short, front-loaded sentence with the mutation signal first and the required inputs stated early. The trailing 'project.create.' is dead weight but the overall footprint is efficient.

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 7-parameter mutation with no output schema, the description leaves too much unexplained: optional field meaning, defaults, and what is returned (e.g. new project id) are all absent. An agent can call it, but only by guessing at the optional fields.

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?

It restates 'name and customer are required', which the schema's required array already declares, and says nothing about the five optional fields (hour_price, vat_percent, start_date, end_date, currency_code). With schema coverage at 57% and vat_percent/currency_code having no descriptions at all, the description fails to compensate for the 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 and resource ('create a project') and scopes it to a customer, so it is clearly distinguishable from the read-side sibling fastbill_list_projects. The trailing 'project.create.' is a redundant internal tag that adds no clarity, keeping it short of a 5.

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?

No guidance on when to use this versus alternatives such as fastbill_create_customer or when a project should be created at all. The 'WRITE:' prefix hints at a mutation but there are no prerequisites, exclusions, or routing hints.

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