USASpending.gov

autocomplete_psc

Read-only

Autocomplete lookup for Product/Service Codes (PSC).

Use exact four-character codes ('R499', 'D302') or description keywords
('professional', 'application'). Returns matching PSC entries with
code and description. Two-character families such as 'D3' can return
no autocomplete matches even when their descendant codes exist.
For partial PSC families or prefix expansion, use get_psc_filter_tree()
instead: path='Service/D/D3/' lists the D3 descendants; start with
path='Service/A/' to discover and drill into an AJ family.

Minimum 2 characters required. Single-character queries return first-N
alphabetical results from the upstream API (useless for matching) and
empty strings return HTTP 400.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "search_text": "<search_text>"
    },
    "name": "autocomplete_psc"
  }
}

Input Schema

Name	Required	Description	Default
`limit`	No
`search_text`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 21, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Goes well beyond the readOnly/openWorld annotations by disclosing quirks an agent could not otherwise know: two-character families may return zero matches despite existing descendants, single-character queries silently return first-N alphabetical results, and empty strings raise HTTP 400. These are exactly the failure modes an agent needs to avoid.

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

Conciseness4/5

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

Front-loaded with the core verb, then usage, then behavioral caveats; every sentence carries operational value. Slightly dense, and the trailing 'Service/A/' drill-down example borders on extraneous, but nothing is filler.

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?

Output schema exists, so return values need only a light mention (matching entries with code and description), which it provides. Combined with the edge-case handling and alternative routing, an agent has everything needed to call this correctly.

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?

With 0% schema coverage the description must compensate, and it thoroughly documents search_text (exact codes, keyword matching, minimum 2 characters, single-char and empty-string edge cases). The limit parameter is never mentioned, so its meaning and default must be inferred from the schema title alone.

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?

The description states a specific verb+resource ('Autocomplete lookup for Product/Service Codes') and immediately names the sibling it is not (get_psc_filter_tree) with the exact condition that selects it. An agent can distinguish this from other autocomplete_* tools and the PSC tree tool without opening any 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 covers when to use this tool (exact 4-char codes or description keywords), when not to (partial families, prefix expansion), and gives a concrete alternative with example paths ('Service/D/D3/', 'Service/A/'). Usage boundaries and exclusions are fully specified.

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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