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

Annotations cover the safety profile (idempotent, non-destructive, closed-world), and the description layers on genuinely new behavioral facts: all-or-nothing atomic rejection when an immutable field is passed, and the cross-tool identity constraint shared with update_field/update_function. This is context the agent could not get from structured fields alone.

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?

Front-loads what the tool does, then the immutability constraint, then the recovery workflow — a logical order with no filler. The multi-step workaround sentence is dense but each clause carries necessary routing information, so it earns its length.

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 9-param mutation tool with no output schema, the description covers the key hazards (immutability, atomic rejection, alternatives) and annotations cover the rest of the safety profile. It omits what a successful response looks like, which is a minor gap given no output schema is declared.

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 coverage is 56%, so descriptions here do part of the work: the immutable fields and the enabled kill-switch are already documented in the schema itself. The description restates the immutability rule and groups the updatable fields but adds no format, valid-value, or naming detail (e.g. auth enum semantics, label length) beyond the schema, so this lands at the mid baseline.

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 (update) and resource (custom endpoint route) and enumerates exactly which attributes are mutable (auth mode, execution mode, enabled state, metadata). An agent can distinguish it from list_endpoints, create_endpoint and delete_endpoint immediately.

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?

Explicitly warns that entity_id/action/method are immutable and that passing them rejects the call, then names the alternative workflow (create_endpoint + create_function + delete_function + delete_endpoint) for changing those fields. This is a textbook when/when-not with an alternative path spelled out.

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