timer_cancelCancel a pending timer using the id returned by timer_schedule. The id is the authorization: holding it is what proves you scheduled the timer, so keep it secret. Already-delivered or already-cancelled timers return cancelled=false.
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | The timer id returned by timer_schedule. |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the annotations (destructive, idempotent), the description adds critical context: the id acts as authorization and must be kept secret, and that already-delivered or already-cancelled timers return cancelled=false, explaining the idempotency behavior in practical terms.
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 sentences, each with a distinct purpose: action, security caveat, and edge-case behavior. No wasted words, and the most important action is front-loaded.
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?
The tool is simple (one parameter, no output schema) and annotations cover safety. The description provides all necessary operational details: cancellation action, id source, secret handling, and behavior for non-pending timers, making it fully self-sufficient.
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?
The schema already covers the id parameter fully (100% coverage), so baseline is 3. The description adds extra meaning by framing the id as a secret authorization token returned by timer_schedule, which is valuable semantic information 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?
The description clearly states 'Cancel a pending timer using the id returned by timer_schedule' with a specific verb and resource, distinguishing it from siblings like timer_schedule and timer_status by focusing on the cancellation action.
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 description implies when to use this tool (to cancel a pending timer) and references the id from timer_schedule. It does not explicitly name alternatives, but the context is clear enough; the edge-case note about already-delivered/cancelled timers provides additional operational context.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
Each tool has a unique, clearly defined purpose (counters, cron, DNS, email, fixtures, webhooks, KV, locks, name checks, regex, timers, timezone, URL checks). There is no functional overlap; even closely related tools like timer_schedule and cron_next are clearly separated by descriptions.
The dominant naming pattern is <resource>_<action> (e.g., inbox_create, kv_get, lock_acquire, tz_convert). A few tools deviate, such as counter_next and cron_next (resource_qualifier), fixture_rows (resource_noun), and request_tool (verb_noun), but these are minor and do not obscure the overall pattern.
At 24 tools, the server exceeds the typical 3-15 range, leaning heavy. The tools cover many independent utility categories, each with a minimal set of operations, but the overall count feels slightly excessive for a single server, though it is justified by the broad scope.
The server provides complete lifecycles for its functional areas: KV (set/get/list/delete), inbox (create/poll/delete), locks (acquire/release), timers (schedule/status/cancel/verify). Each utility is self-contained, and the request_tool offers a path for extending the surface. No obvious gaps or dead ends within the intended domain.