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lkcair

yfinance-ai MCP server

by lkcair

get_isin

Read-onlyIdempotent

Retrieve the International Securities Identification Number (ISIN) and related identification data for a given stock ticker symbol.

Instructions

Get International Securities Identification Number (ISIN) for a ticker.

Args: ticker: Stock ticker symbol

Returns: ISIN code and related identification information

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
tickerYes

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

C2.8/5.0
Behavior2/5

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds almost nothing beyond that – no mention of external data sources, latency, or failure behavior for an openWorld lookup, and the 'Returns' line merely restates what the output schema provides.

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?

Short and front-loaded with the core purpose in the first sentence. The Args/Returns block is boilerplate scaffolding that does little work given the schema and output schema already exist.

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

Completeness3/5

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

For a single-parameter lookup with an output schema, the description need not explain return values, and it doesn't. However, it omits any routing guidance among the large set of get_* siblings, which is the main gap.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must carry the burden, but 'ticker: Stock ticker symbol' only restates the parameter name. It gives no format expectations (case, exchange suffix, ambiguity handling) that an ISIN lookup would benefit from.

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?

States a specific verb (get) and resource (ISIN) scoped to a ticker, and the acronym is expanded. It does not differentiate from any sibling, but ISIN is a unique lookup that no sibling covers.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool versus alternatives such as validate_ticker or search_ticker, nor any prerequisite or constraint. The agent must infer usage entirely.

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