Lists Pub/Sub subscriptions across all topics and detached ones, including delivery type, filter, dead-letter topic, and backlog; filter by topic to inspect a specific subscription set.
Every Pub/Sub subscription (of every topic, and detached ones) with its delivery type, filter, dead-letter topic and backlog.
| Name | Required | Description | Default |
|---|---|---|---|
| topic | No | Only this topic's subscriptions (id or full name) |
Changes observed during successful MCP inspections.
v0.2.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It usefully discloses what the response contains (delivery type, filter, dead-letter topic, backlog) and that detached subscriptions are included, but says nothing about pagination, ordering, cost on large projects, or required permissions.
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?
One dense sentence with the scope and return fields front-loaded and no filler. It is a fragment rather than a sentence, but nothing in it is wasted.
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 single-optional-parameter read tool with no output schema, the description covers scope, filtering semantics via the schema, and the key fields returned. Only pagination and permissions remain unaddressed, which is a minor gap.
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%, so the baseline is 3; the description adds genuine meaning by making clear that omitting the 'topic' parameter returns subscriptions across all topics plus detached ones, which the schema does not state.
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 description names the resource (Pub/Sub subscriptions), states the scope ('every topic, and detached ones'), and enumerates the payload fields (delivery type, filter, dead-letter topic, backlog). It is clearly distinct from pubsub_list_topics by resource, though it never names that sibling explicitly.
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?
Listing subscriptions is the implied use and the optional 'topic' filter is self-explanatory from the schema, but there is no explicit when-to-use guidance, no mention of pubsub_list_topics or pubsub_peek as alternatives, and no note about when to omit the filter.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.