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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the bar is lower, but the description adds essentially nothing behavioral: it does not mention that results are paginated, that limit/offset must be chained via next_offset, or that calls consume FastBill's hourly quota. "project.get" is only a bare internal endpoint reference.

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 short fragments, front-loaded with the verb and resource; nothing is padded. It loses a point because the trailing "project.get." is cryptic and the terse parenthetical reads more like a dump of fields than structured guidance.

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?

With no output schema, listing the returned fields is genuinely useful and the tool is a simple read with no required params. However, pagination mechanics and the purpose of the two ID filters are unexplained, which for a quota-limited paged endpoint leaves a real gap.

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 50%: limit and offset are well documented in the schema, but project_id and customer_id have no descriptions anywhere. The parenthetical lists return fields (name, customer, rate, VAT, dates) rather than parameters, so it does not compensate for the undocumented filters an agent would want to know are available for narrowing results.

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?

Specific verb + resource ("List projects") plus a parenthetical of the fields returned and the underlying API endpoint (project.get). It is distinct from fastbill_create_project and the other list_* siblings, though it never names a sibling to route against.

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 statement of when to use this vs. alternatives (e.g., filtering a single project vs. listing all), no prerequisites, no mention of when the optional project_id/customer_id filters should be applied. The agent is left to infer usage from the schema alone.

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