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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the description's credit is for the extras: it restates that sequences are built and switched on by a person in Postkey (i.e., no create/enable path here) and discloses the result cap of 50 and the field set. It does not say what to do when there are more than 50 sequences or whether the list is paginated or ordered.

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?

Two sentences, front-loaded with the action and resource, with no filler. The parenthetical definition and the returned-field list are dense but each clause earns its place; the enumeration makes the first sentence long but not padded.

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?

An output schema exists, so the description doesn't owe return-value documentation, yet it still sketches the fields. For a zero-parameter read tool with a follow-up pointer, the only real omission is what happens past the 50-item limit, which matters if the profile has many sequences.

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 tool takes zero parameters, so the baseline is 4; there is nothing for the description to disambiguate. The reference to passing "an id" to postkey_list_sequence_subscribers usefully implies where the ids in the response come from.

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?

Specific verb+resource ("Lists the profile's DM sequences") plus a parenthetical defining what a sequence is, and an explicit enumeration of the returned fields and the 50-item cap. It is distinguishable at a glance from postkey_list_automations and from postkey_list_sequence_subscribers, which it names.

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 states this is read only and points to postkey_list_sequence_subscribers as the drill-down, giving clear next-step routing. It stops short of explicitly contrasting with sibling list tools such as postkey_list_automations or stating when a caller would not need this list.

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