The verdict in three sentences
Built by a Tunis team in 2026, a documented public REST API in OpenAPI format for a B2B platform costs TND 60,000 to 140,000 ex. VAT (roughly EUR 17,500 to 41,000), developer portal and security included, against EUR 80,000 to 180,000 for the same scope in Berlin. Development is only half the effort: governance (versioning, quotas, deprecation, support) decides whether the API becomes a sales lever or a permanent burden. With a 99.5% SLA and per-call pricing, a well-scoped API can cover its running costs from 15 to 25 integrated customers.
The budget for a public API, module by module
For a fleet management platform exposing vehicles, trips, fuel use and alerts to customer ERPs, here are 2026 ranges from Tunisian team quotes, with a Berlin benchmark.
| Module | Content | Tunis 2026 (TND ex. VAT) | Berlin 2026 (EUR, indicative) |
|---|---|---|---|
| API design | Resource model, OpenAPI 3.1 spec, review | 8,000 to 18,000 | 10,000 to 22,000 |
| Endpoint development | 25 to 40 REST endpoints, pagination, filters | 22,000 to 50,000 | 30,000 to 65,000 |
| Authentication and security | API keys, OAuth 2.0, rate limiting, logging | 9,000 to 20,000 | 12,000 to 25,000 |
| Webhooks | Events (fuel alert, geofence entry), replay | 6,000 to 14,000 | 8,000 to 18,000 |
| Developer portal | Interactive docs, sandbox, key management | 10,000 to 25,000 | 12,000 to 32,000 |
| Testing and acceptance | Contract tests, load tests, API pentest | 5,000 to 13,000 | 8,000 to 18,000 |
| Total project | Delivery in 4 to 6 months | 60,000 to 140,000 | 80,000 to 180,000 |
In operation, plan TND 2,500 to 6,000 a month (EUR 730 to 1,750) for hosting, the API gateway (Kong, Tyk or a cloud service) and monitoring, plus half to one full-time person for developer support.
Governance: the rules that prevent debt
A public API commits the vendor to dozens of integrations it does not control. Every unmanaged change breaks a customer ERP. Decisions to document before launch:
| Rule | Recommended choice | Impact |
|---|---|---|
| Versioning | Version in the URL (/v1/), breaking changes only in a major version | Predictability for integrators |
| Deprecation | At least 12 months' notice, Sunset header | No surprise breakage |
| Default quotas | 60 requests per minute, 50,000 per day on the standard plan | Platform protection |
| SLA | 99.5% monthly uptime, so 3 h 39 min maximum downtime | Credible contractual commitment |
| Support response time | Within 1 business day, 4 h on premium | Controlled support cost |
| Changelog | Public, dated, with migration guide | Developer trust |
| Sandbox | Dummy data, reduced quotas, free | Faster integration |
A 99.9% SLA (43 minutes of downtime a month) requires a redundant multi-zone architecture that can double hosting costs. For a mid-sized B2B platform, 99.5% is the balance point.
Monetising the API without exploding support cost
Three models dominate in 2026: API included in the premium subscription, tiered per-call billing, or a one-off integration fee. For fleet management, the hybrid model works well: an included tier (for example 100,000 calls a month), then TND 15 to 30 (EUR 4.40 to 8.80) per block of 10,000 calls. The hidden cost is support: without quality documentation, each new integrator consumes 10 to 20 hours of assistance. A developer portal with code samples and a sandbox brings that down to 2 to 4 hours.
Mini case study
Yassine, head of product at a Tunisian fleet management platform (2,400 tracked vehicles, 85 customers, several in Germany), loses tenders for lack of connection to carriers' ERPs.
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- Public API project: TND 95,000 ex. VAT (about EUR 27,800), plus TND 4,000 a month in running costs and half a support role (TND 2,500 a month).
- Pricing: API add-on at TND 450 (about EUR 130) a month per customer, extra calls beyond 100,000.
- Target: 20 customers on the add-on within 12 months, so TND 9,000 a month in revenue.
- Monthly running cost: TND 6,500. Margin of TND 2,500 a month, plus contracts won thanks to the integration: two tenders worth TND 60,000 a year each are enough to repay the project in under 12 months. A Berlin build of the same scope would have cost around EUR 120,000, more than four times as much.
FAQ
How much does a public API for a B2B platform cost?
Between TND 60,000 and 140,000 ex. VAT in Tunis in 2026 (about EUR 17,500 to 41,000), depending on endpoints, webhooks and the developer portal. A first 15-endpoint version can start around TND 45,000.
Why use OpenAPI?
The OpenAPI specification generates interactive documentation, client SDKs and contract tests. It roughly halves your customers' integration time.
What SLA should we promise?
99.5% monthly uptime is realistic for a mid-sized platform, so 3 h 39 min maximum downtime. Moving to 99.9% can double hosting costs.
Should API access be billed?
It is advisable as soon as volumes vary widely between customers. An included tier then TND 15 to 30 per 10,000 calls covers infrastructure and support costs.
How long does it take to launch the API?
As a 2026 order of magnitude, 4 to 6 months, including 3 to 4 weeks of design. A pilot with 2 or 3 customers before public release avoids breaking changes in version 1.
Let's scope your project. Describe the resources to expose, your target customers and volumes: we price the API, developer portal and governance model on a 4 to 6 month schedule. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
