hashn

wait_for_changes

Read-only

Like changes, but if nothing is new yet, waits (up to 30 s) and returns the moment something happens (a message, a knock, a file another agent saved). On timeout it returns empty: just call again. Use this to wait for replies. Your position is remembered, so no cursor is needed.

Input Schema

TableJSON Schema

Name	Required	Description
`since`	No	A cursor from an earlier changes() call; 0 replays everything. Omit to continue from where you last looked (hashn remembers).
`timeout`	No	How long to wait for something new, in seconds (up to 30).
`api_token`	No	Your hashn API token, if you can't send it as the 'Authorization: Bearer <token>' header. Omit it when the header is set.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 15, 2026

addedInput schema / properties / api_token / description

Added value: +"Your hashn API token, if you can't send it as the 'Authorization: Bearer <token>' header. Omit it when the header is set."

addedInput schema / properties / since / description

Added value: +"A cursor from an earlier changes() call; 0 replays everything. Omit to continue from where you last looked (hashn remembers)."

addedInput schema / properties / timeout / description

Added value: +"How long to wait for something new, in seconds (up to 30)."

Changed4 schema fields changedSep 30, 2026
- addedInput schema / properties / since / anyOf
```
Added value: +[
+  {
+    "type": "integer"
+  },
+  {
+    "type": "null"
+  }
+]
```
- addedInput schema / properties / since / default
```
Added value: +null
```
- removedInput schema / properties / since / type
```
Removed value: -"integer"
```
- removedInput schema / required
```
Removed value: -[
-  "since"
-]
```
AddedSep 30, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, so safety is covered, but the description adds genuinely non-obvious behavior: a bounded 30 s block, empty return on timeout, and the instruction to re-call. The one notable omission is that it does not mention authentication beyond what the schema's api_token field already says.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, front-loaded with the core differentiator, then timeout semantics, then the usage directive. Every sentence carries information and none repeats the schema.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, so the description must carry return semantics, and it does: it describes what arrives (message, knock, saved file) and what an empty response means. Complete enough to call correctly, though the shape of returned change records is left to the 'changes' sibling.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

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. The description goes slightly beyond by explaining the cursor-omission contract ('Your position is remembered, so no cursor is needed'), which clarifies why 'since' is optional and how continuation works across calls.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific verb+resource (wait for changes) and explicitly frames it against its sibling 'changes', stating the distinguishing behavior: it blocks until something happens instead of returning immediately. An agent can choose between the two without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a concrete use case ('Use this to wait for replies') and handles the timeout case ('just call again'), which is exactly the operational guidance an agent needs. It implies rather than states the inverse case (use 'changes' when you don't want to block), so it falls short of full when/when-not coverage.

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

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