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

Goes well beyond the annotations by disclosing that the entry is unbilled until invoiced and, critically, that each call consumes API credits (create 10, invoice 50) against a limited monthly quota — the kind of cost/rate-limit information an agent cannot get from readOnlyHint/destructiveHint alone. The mutation framing is also consistent with readOnlyHint=false, so no contradiction.

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 short sentences with the operation type front-loaded as "WRITE:", followed by billing semantics and cost. No filler, no repetition of schema fields, and the highest-stakes information (credit cost) is placed where it will be read.

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 full schema coverage and clear annotations, the description supplies the missing non-schema context: costs, quota, and billing status. The only gap is that with no output schema it does not say what comes back (presumably the created time entry and its id), leaving the agent unsure how to reference the entry afterwards.

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 every parameter (task_id, user_id, entry_date, started_at_time, ended_at_time, comments, unbillable) is already documented with format hints and source tools. The description adds only the "on a task" framing, which slightly reinforces task_id's importance but adds no new format, default, or constraint detail. Baseline 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?

Names a specific verb+resource combination ("record a time entry") and narrows scope with "on a task", so an agent can immediately tell this creates a task-linked time entry rather than a project, invoice, or person. It stops short of explicitly contrasting with siblings like papierkram_get_time_entry or papierkram_list_time_entries, relying on naming convention for that separation.

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?

The leading "WRITE:" tags this as a mutation and the "Not billed until an invoice is made" line implies when the record matters downstream, but there is no explicit statement of when to prefer this over the get/list time-entry siblings or what prerequisites (task must exist, user must exist) are assumed. Usage is inferable but not spelled out.

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