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

Beyond the annotations (destructiveHint=true, idempotentHint=true), it discloses non-obvious behavior: re-setting replaces the events, remove:true detaches the destination, and a Claude routine is rate-limited to once per event and at most 25 times an hour. This is exactly the extra context annotations cannot carry.

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?

The purpose and the key constraint (destinationName is a name, not an address) are front-loaded, and each clause carries information. It is a dense single paragraph that could be broken up for scanability, which keeps it from a 5.

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 6-parameter mutation tool with no output schema, the description supplies everything an agent needs: id sources per jobType, event semantics, replacement/detach behavior, and rate limits. No gaps remain that would cause a mis-call.

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?

It adds meaning beyond the 67% schema coverage: destinationName is 'a name... never an address', entrypointId 'limits it to one entrypoint', and the events semantics for alerts (alert fires or recovers, failed means the check could not run) go well past the bare enum. Only remove:true is essentially repeated from 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 opening sentence states a specific verb and resource ('Make a job call a registered destination when it fails, finishes, or its alert fires') plus a concrete example. It is the only callback-setting tool among the siblings, and the description makes its role unambiguous without opening any schema.

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?

It routes the agent to the correct source tools for each id (fastero_list_callback_destinations, fastero_list_python_projects, fastero_list_schedules) and explains the two jobType paths. It does not explicitly state when not to use the tool, but with no direct sibling alternative the contextual guidance is strong.

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