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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds genuine context beyond that: the fields carried by each entry (customer, totals, dates, payments) and the backing endpoint 'revenue.get', which helps an agent anticipate the shape of results for a tool with no output schema.

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 sentences plus an endpoint tag; the resource, its contents, and the filter analogy are all front-loaded with no filler.

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 8-parameter, all-optional list tool with annotations covering safety and no output schema, the description supplies purpose, return fields, and a filter cue, which is close to sufficient. It leaves minor gaps around how multiple filters combine and how results are ordered.

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 75% and pagination parameters (limit, offset) are well documented in the schema, so the baseline is 3. The description's 'same filters as invoices' hints at the filter family but adds no meaning for the undocumented customer_id and invoice_number parameters or for how date and paid-date ranges combine.

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 ('List revenue entries') and disambiguates the domain with a parenthetical ('income booked in FastBill'), plus the underlying API service ('revenue.get'). It is clear what the tool returns, though it never explicitly contrasts with the near-sibling fastbill_list_invoices beyond noting shared filters.

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?

'Takes the same filters as invoices' implies a relationship to fastbill_list_invoices and gives a usable mental model for filtering. However, it does not state when to choose revenues rather than invoices, expenses, or list_customers, nor any exclusions, so usage is only implied.

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