bls-labor-mcp-server

Get Latest BLS Observation

bls_get_latest

Read-onlyIdempotent

Return the single most recent observation for one or more BLS series. Use for "what is X right now" questions — the current unemployment rate, the latest CPI reading, etc. Each series consumes one API query against the 500/day limit; for the current value of many series, bls_get_series with a 1-year window is more quota-efficient (one query for up to 50 series). Recommended limit: 10 series; maximum: 50.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`series_ids`	Yes	One or more BLS SeriesIDs (1–50). Each consumes one daily API query. Use bls_search_series to resolve concepts to SeriesIDs. Recommended: ≤10 series.

Output Schema

TableJSON Schema

Name	Required	Description
`error`	No	Present when the call failed. Absent on success.
`failed`	No	Series that failed to fetch. Inspect seriesId and error for per-item details. Not-found series appear here rather than as a tool-level error.
`notice`	No	Guidance when one or more series failed — e.g. to use bls_search_series to verify SeriesIDs. Absent when all series returned data.
`results`	No	Successfully fetched series with their latest observations. Series that failed appear in failed[] instead.
`succeeded`	No	Number of series with a successfully fetched observation.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 22, 2026

changedOutput schema / properties / failed / items / properties / error / description

Previous value: -"Error message. Common values: \"Series does not exist\" (invalid SeriesID — use bls_search_series to find valid IDs), \"No observations returned\" (series exists but has no current data)."New value: +"Error message. Common values: \"Series does not exist\" (invalid SeriesID — use bls_search_series to find valid IDs), \"No observations returned\" (series exists but has no current data). BLS does not always name the series it rejected: an invalid SeriesID sometimes comes back as the generic \"Your request has failed. Please check your input parameters, and try your request again.\", which means the same thing here."

Changed3 schema fields changedAug 31, 2026

addedOutput schema / properties / results / items / properties / latestObservation / properties / available

Added value: +{
+  "description": "False when BLS published the \"-\" missing-value sentinel for this period.",
+  "type": "boolean"
+}

changedOutput schema / properties / results / items / properties / latestObservation / properties / value / description

Previous value: -"Observation value as a string, matching BLS API output. Parse to float for arithmetic."New value: +"Raw observation value from BLS. The literal \"-\" means unavailable; check available before arithmetic and read footnotes for the reason."

changedOutput schema / properties / results / items / properties / latestObservation / required

Previous value: -[
-  "year",
-  "period",
-  "value"
-]New value: +[
+  "year",
+  "period",
+  "value",
+  "available"
+]

Changed6 schema fields changedAug 24, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedInput schema / additionalProperties
```
Added value: +false
```

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedOutput schema / anyOf

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "results",
+      "succeeded",
+      "failed"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

addedOutput schema / properties / error

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `invalid_api_key`: BLS rejected the configured BLS_API_KEY as invalid. `quota_exceeded`: The BLS API 500 query/day limit has been reached. `series_locked`: The BLS database is temporarily locked for the requested series. Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "invalid_api_key",
+            "quota_exceeded",
+            "series_locked"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

removedOutput schema / required

Removed value: -[
-  "results",
-  "succeeded",
-  "failed"
-]

Changed2 schema fields changedJun 8, 2026

changedOutput schema / properties / results / description

Previous value: -"Latest observation for each requested series, in request order."New value: +"Successfully fetched series with their latest observations. Series that failed appear in failed[] instead."

changedOutput schema / properties / results / items / properties / latestObservation / description

Previous value: -"Most recent observation. Absent when the series returned no data."New value: +"Most recent observation."

Changed3 schema fields changedJun 4, 2026

changedOutput schema / properties / failed / description

Previous value: -"Series that failed to fetch, with per-item error details."New value: +"Series that failed to fetch. Inspect seriesId and error for per-item details. Not-found series appear here rather than as a tool-level error."

changedOutput schema / properties / failed / items / description

Previous value: -"A series that could not be fetched."New value: +"A series that could not be fetched, e.g. due to an invalid SeriesID or empty data window."

changedOutput schema / properties / failed / items / properties / error / description

Previous value: -"Error message."New value: +"Error message. Common values: \"Series does not exist\" (invalid SeriesID — use bls_search_series to find valid IDs), \"No observations returned\" (series exists but has no current data)."

Changed1 schema field changedMay 30, 2026

addedOutput schema / properties / notice

Added value: +{
+  "description": "Guidance when one or more series failed — e.g. to use bls_search_series to verify SeriesIDs. Absent when all series returned data.",
+  "type": "string"
+}

First observedMay 25, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Annotations already mark it read-only and idempotent, and the description adds useful behavioral context: each series consumes one API query against a 500/day limit, and the tool recommends a 10-series limit to manage quota. This goes beyond what the annotations convey and helps with call planning.

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 focused sentences carry purpose, usage guidance, quota behavior, alternatives, and limits. The description is front-loaded and every sentence earns its place.

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

Completeness5/5

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

With one parameter, a full input schema, an output schema, and safety annotations, the description covers the essential selection criteria, quota impact, and the relevant alternative. Nothing critical is missing for correct invocation.

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

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema has 100% coverage for the single series_ids parameter, including types, bounds, and the recommendation to use bls_search_series. The description mostly restates this information, so it adds little new parameter-level meaning; the baseline 3 applies.

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?

States a specific verb and resource: 'Return the single most recent observation for one or more BLS series.' It also distinguishes itself from the sibling bls_get_series by noting the quota-efficiency tradeoff, so an agent can tell them apart without opening the schema.

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

Usage Guidelines5/5

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

Explicitly orients the tool to 'what is X right now' questions and names bls_get_series as the better alternative when many series are needed. It also provides concrete limits (recommended 10, maximum 50), giving clear selection criteria.

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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