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), and the description adds real behavioral value: the default no-filter behavior scopes results to the current month's latest entries. It omits quota/pagination behavior, though the limit parameter's schema text covers the API quota.

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 front-loaded sentences that carry the field list and default behavior with no filler. The trailing "time.get." endpoint token is jargon that does not earn much space but costs little.

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, the inline field enumeration is genuinely useful compensation, and the default-month behavior is disclosed. However, for an 8-parameter filter tool with 3 undocumented id filters and an ambiguous date/start_date/end_date triad, the description leaves real gaps.

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?

At 63% schema coverage, the schema already documents date, limit, offset, start_date and end_date. The description only hints at filtering ("without filters") and does not explain the undocumented time_id, project_id, and customer_id filters or clarify date vs date-range, so it adds little beyond 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?

Specific verb+resource ("List work time entries") with an enumeration of the fields returned, which lets an agent distinguish it from fastbill_create_time_entry and the other list_* siblings. It does not explicitly name a sibling alternative, keeping it out of 5 territory.

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?

"Without filters FastBill returns the latest entries of the current month" implies how to call it and what happens with an empty filter set, but there is no explicit when-to-use or when-to-prefer-another-tool guidance, and no explanation of when to use date vs start_date/end_date.

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