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

Annotations declare readOnlyHint=true, so safety is already covered. The description adds a genuine hard constraint not present in the schema ('At least one filter is required') and discloses the return shape (field list) plus the underlying endpoint GET /api/entries, which is real value beyond the annotation.

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 tight sentences, front-loaded with the returned fields followed by the key constraint and then parameter behavior. The field enumeration is long but earns its place given there is no output schema; little waste overall.

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 read-only list tool with no output schema, the description covers purpose, the required-filter rule, key filter semantics, and the return fields. The main omission is absence of any guidance on selecting this tool versus adjacent timer/entry tools, which leaves a small 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 description coverage is 100%, so all 11 parameters are already documented, including the truncation caveat on limit and operators on where. The description's 'from/to filter by the entry's time interval' and 'running_only=true returns running timers' largely restate schema text, so the baseline of 3 applies.

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 time entries') and enumerates the fields it returns (id, task_id, user_id, project_id, start/end time, duration, description, billed), which is well beyond a restatement of the name. It does not explicitly contrast itself with siblings such as paymo_list_tasks or paymo_update_time_entry, but the resource is unambiguous.

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?

Gives one concrete usage rule ('At least one filter is required') and explains what from/to and running_only do, which is useful context. However, it never states when to prefer this tool over alternatives like paymo_start_timer, paymo_stop_timer, or paymo_update_time_entry, so selection guidance is implied rather than explicit.

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