--- title: "Tool call" summary: "A tool call is a single invocation of an exposed operation by a model or agent, with structured arguments and a structured result — the unit that is authenticated, metered and audited." canonical_url: https://entitybind.com/glossary/tool-call last_updated: 2026-10-15 copy: full --- # Tool call > A tool call is a single invocation of an exposed operation by a model or agent, with structured arguments and a structured result — the unit that is authenticated, metered and audited. Canonical page: https://entitybind.com/glossary/tool-call Last updated: 2026-10-15 Glossary · Interfaces ## How to read this The definition as the field writes it comes first, weaknesses and all. What Entity Bind does about it comes last, in its own paragraph, so you can take one without the other. [Filed under interfaces](https://entitybind.com/glossary#integration). By [James Rooney](https://entitybind.com/about), founder of Entity Bind · Last revised 15 October 2026 ## What tool call means In an agentic system the tool call is the boundary between reasoning and action. Everything before it is a model's proposal; the call is what actually reads a database, spends money or writes a record. Treating it as the unit of accounting rather than treating the whole conversation as one is what makes an agent's behaviour reviewable afterwards. Three properties are worth designing for. A call should be idempotent or carry an idempotency key, because agents retry. Its result should be structured rather than prose, so the next step branches on a field instead of on a parsed sentence. And its cost should be predictable, so an agent looping over a file cannot produce a surprising bill. The most important design question for a resolution tool is what it returns when it does not know. A tool that always returns a best guess with a score forces the agent to invent a threshold, which it will do badly and inconsistently. A tool that returns a distinct unresolved outcome lets the agent branch on the decision itself: act on a match, escalate or enrich an abstention, stop on a non-match. Entity Bind's tools return the decision rather than a similarity score, and the credit rule follows the work done: one credit for a decision reached deterministically or probabilistically, five where LLM adjudication or agentic research was needed, and zero for an abstention, a byte-identical replay, or an input that normalised to no identifying signal. Branch on the decision first and evaluate any stricter confidence policy against labelled records. Confidence bounds depend on the recorded evidence population; there is no universal score for every match. Read match_confidence_basis and the evidence. A 0.99 filter can return some v8 adjudicated matches while excluding valid identifier matches, so validate its coverage cost on your own inputs. ## Where this shows up in Entity Bind Three pages where this term stops being vocabulary and starts changing an answer, a payload or a price. - [The MCP server](https://entitybind.com/mcp): Eleven tools over the Model Context Protocol, on the same credentials, tenancy, rate limits and credit rule as the HTTP API. - [The API reference](https://entitybind.com/api): The REST surface: payloads, the decision outcomes, the error model, the usage block and the ceiling on the confidence field. - [Pricing and the credit rule](https://entitybind.com/pricing): What a decision costs, what a deep attempt costs, and the three things that cost nothing at all. The fastest way past a definition is a file: which of your rows are the same company, which of your existing matches we would not have made, and what we could not decide. [Start free →](https://app.entitybind.com/app?signup=1) ## The terms next to this one Each with its own sentence, because the next question is usually about the word beside this one. - [MCP (Model Context Protocol)](https://entitybind.com/glossary/mcp): The Model Context Protocol is an open standard for connecting AI assistants to external tools and data, so that a model can call a system's real operations instead of being told about them in a prompt. - [Abstention](https://entitybind.com/glossary/abstention): An abstention is a first-class 'we do not know' returned instead of a match: the record comes back unresolved, with a ranked shortlist, a typed reason and the column that would have decided it. - [Idempotency](https://entitybind.com/glossary/idempotency): An operation is idempotent when performing it repeatedly has the same effect as performing it once, which is what makes a retry after a timeout safe rather than duplicating work. - [Replay](https://entitybind.com/glossary/replay): Replay is re-serving a previous decision for byte-identical content rather than recomputing it, which makes repeated submissions free and deterministic — provided the replayed decision is still one the system would stand behind. - [Confidence floor](https://entitybind.com/glossary/confidence-floor): A confidence floor is the score below which a system refuses to return a match at all, expressed as an acceptance contract rather than as a promise about accuracy. - [Decision receipt](https://entitybind.com/glossary/decision-receipt): A decision receipt is the durable, retrievable record of why a particular match was made — the features, the probability, the thresholds in force, the sources cited and the version of the pipeline that decided — addressable by an identifier returned with the answer. ### Answered at length elsewhere - [Entity resolution for AI agents](https://entitybind.com/guides/entity-resolution-for-ai-agents) (Guide): An agent about to pay or contract a counterparty needs a decision with a receipt, not a similarity score. Why abstention is the safe default for an autonomous caller, and what the MCP surface exposes. - [AI agents](https://entitybind.com/use-cases/ai-agents) (Use case): A counterparty check before the agent acts, and a receipt for what it acted on. - [Claude Code](https://entitybind.com/integrations/claude-code) (Integration): Claude Code reads MCP servers from an mcpServers object, so a URL and a bearer token are the whole configuration. Eleven tools then appear in the session. - [Entity binding failures in AI agents](https://entitybind.com/guides/entity-binding-failures-in-ai-agents) (Guide): An entity binding failure is an agent calling the right tool on the wrong real-world entity. What a 2026 study of 1,800 runs found, and four safeguards. ## The other term on this shelf How a program or an agent reaches a resolver, and what a call costs. - [MCP (Model Context Protocol)](https://entitybind.com/glossary/mcp) Previous, alphabetically: [Ticker symbol](https://entitybind.com/glossary/ticker) · Next, alphabetically: [Transliteration](https://entitybind.com/glossary/transliteration) ## Evidence basis Internal fixtures only. The historical 2026-08-29 per-tier recording covers 317 GB companies with identifier-rich arrivals seeding the catalogue first; the context tier includes country and registered-town prose. Its legacy replay has no full-prompt-verified calls and cannot certify current calibration. The September 5 CI reports cover 1,176 labelled pairs and 705 records over 250 companies using offline stubs. These are not independent customer holdouts or live production validation; the 99% minimum-input product target remains unmet. Scope is company and organisation identity only — not people, vessels, bank-account ownership, sanctions or emissions. Results may not be used for eligibility decisions about individuals, including employment, credit and tenancy. ## Start with your own company records. Create your workspace, verify your email and run your first company file. The Free plan needs no card. Create API keys in your workspace when you need an integration. [Start free](https://app.entitybind.com/app?signup=1) · [All 64 terms](https://entitybind.com/glossary) 300 credits. No card. For a guided review of your file, explore [the Merge Safety Sprint](https://entitybind.com/audit-pack). --- Entity Bind resolves companies and organisations only. It does not resolve people, vessels, bank-account ownership, sanctions exposure, emissions or geolocation, and its results may not be used for eligibility decisions about individuals, including employment, credit and tenancy. 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