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

Adds real context beyond the annotations: append ordering, no notifications sent, reversibility via delete_group_link, and an explicit instruction that confirmation is unnecessary. That last point sits in mild tension with destructiveHint=true, but since the operation is additive and reversible the description is clarifying rather than contradicting the annotation. Return shape ('the whole new list') is also disclosed, though nothing is said about duplicate links given idempotentHint=false.

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 tight sentences with the action and its placement front-loaded, followed by the authorization and safety facts. The 'as Settings, Links, Add does' analogy is slightly wordy but does convey placement concretely; no sentence 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 3-parameter mutation with no output schema, the description covers authorization, reversibility, notification side effects and the return value ('the whole new list'). Only the duplicate/non-idempotent case and any rate or quota limits are left unaddressed.

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 100% and each of the three parameters carries its own description, including format and maxLength on url and label. The description adds no parameter-level detail beyond the notion of sidebar placement, so the schema is doing the work — baseline 3.

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?

A specific verb and resource ('Add a link to the group's sidebar') that an agent can immediately separate from update_group_link, delete_group_link and list_group_links in the sibling set. The append-position detail ('after the existing ones') further pins down what kind of add this is.

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?

States the authorization gate ('Admins only') and the rollback path ('undone with delete_group_link'), which tells the agent when this is safe versus when to reach for update/delete. It doesn't explicitly contrast with update_group_link for the case where a link already exists, so it falls just short of full when/when-not guidance.

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