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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the write/destructive nature is known without the description; the text correctly aligns with that (create/update is a write). It adds useful domain detail (event vocabulary, payload formats), but says nothing about the HMAC secret, what an update overwrites, or whether saving an existing subscription is reversible.

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 compact sentences, front-loaded with the create-vs-update decision, followed by the two enumerations an agent needs. Every clause carries information; nothing is filler.

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 upsert tool with no output schema, the description covers the create/update branch, the event vocabulary, and the payload formats, which is most of what an agent needs. It is silent on what the call returns (e.g., the subscription id) and on secret/activation handling, both of which matter for a write operation.

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 the baseline is 3, and the description goes slightly beyond it by describing the SLACK payload shape ({"text": "..."}) and contrasting it with GENERIC full JSON, which the enum labels alone do not convey. Field-level details like secret, isActive, and name uniqueness are left entirely to 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?

States a specific verb and resource ('create or update a webhook subscription') and adds a mode discriminator: 'Omit id to create, provide id to update.' That is precise enough for an agent to know exactly what happens. It does not, however, reference the sibling webhook tools (list/get/delete/test) to distinguish itself from them.

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 clear conditional context for the two modes of operation (omit id vs provide id), which is the main selection decision an agent faces here. It does not name alternatives or state exclusions (e.g., when to use _test or _delete instead), so it stops short of full 5-level guidance.

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