perseus

perseus_budget

Read-only

Declare a token budget for the rendered context; enforce prompt size limits with warnings or strict failure, providing a per-directive breakdown when over budget.

Instructions

Declare a token budget for the rendered context (renders as empty text). Enforced by perseus prompt-size: an over-budget render warns — or fails with strict — with a per-directive byte/token breakdown (#606). Declarations are read from source text before conditionals are evaluated; top-level only — a @budget inside an @include'd file is not enforced (prompt-size warns) (#626). Read-only.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "perseus_budget"
  }
}

Input Schema

Name	Required	Description
`max`	No	Value for max parameter
`strict`	No	Value for strict parameter
`forensic`	No	Value for forensic parameter

Schema Changelog

Changes observed during successful MCP inspections.

Addedv1.0.14Jul 7, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Discloses read-only behavior (matches annotation), renders as empty text, enforcement details, and parsing constraints. Adds context beyond the `readOnlyHint` annotation.

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?

The description is concise, front-loaded with purpose, and includes relevant enforcement and constraint details without unnecessary words.

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?

Given the simple tool (3 optional params, no output schema, readOnlyHint), the description covers purpose, enforcement, and placement rules. Does not mention return value, but 'renders as empty text' suffices.

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?

Schema coverage is 100% but parameter descriptions are minimal ('Value for max parameter'). The tool description clarifies that 'strict' causes failure, but does not explain 'max' or 'forensic'. Baseline is 3 due to high coverage, with marginal added value.

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

Purpose4/5

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

The description clearly states the verb 'declare' and resource 'token budget', and explains enforcement by `perseus prompt-size`. It implicitly distinguishes from sibling tools like `perseus_prompt` by focusing on budget declaration, but does not explicitly differentiate.

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?

Provides specific guidelines: declarations are read before conditionals, top-level only, and not enforced inside included files (with a warning). Lacks explicit when-not or alternatives, but the constraints are clear.

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